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Previous Article | Next Article 
Journal of Virology, March 2000, p. 2913-2919, Vol. 74, No. 6
Departments of
Biology1 and Pathology & Molecular
Medicine,3 McMaster University, Hamilton,
Ontario L8N 3Z5, and Department of Medical Microbiology & Immunology, University of Alberta, Edmonton, Alberta T6G
2H7,2 Canada
Received 13 August 1999/Accepted 14 December 1999
Transcripts of most intron-bearing cellular genes must be processed
by the splicing machinery in order to efficiently accumulate and gain
access to the cytoplasm. However, we found that herpes simplex virus
induces cytoplasmic accumulation of both spliced and unspliced
polyadenylated Herpes simplex virus (HSV) is a
large enveloped DNA virus that infects a wide variety of mammalian
cells in tissue culture (reviewed in reference 46).
HSV executes a complex genetic regulatory program during lytic
infection: three temporal classes of viral genes (immediate early
[IE], early [E], and late [L]) are sequentially activated in a
regulatory cascade driven by viral gene products, while expression of
most host cell genes is strongly suppressed. The HSV lytic program is
initiated by the virion transactivator VP16, which acts in combination
with host factors to stimulate transcription of the five IE genes
(reviewed in references 16 and
60). Four of the IE proteins (ICP0, ICP4, ICP22, and
ICP27) then play key roles in orchestrating expression of the viral E and L genes (10, 30, 48, 49, 55, 59, 63).
Early studies demonstrated that the HSV lytic cascade involves both
transcriptional and posttranscriptional controls of mRNA metabolism
(64). Mounting evidence suggests that the immediate-early (IE) protein ICP27 contributes to the posttranscriptional component of
the viral regulatory program (57; reviewed in
reference 51). ICP27 is an essential regulator that
stimulates accumulation of a subset of viral E and L mRNAs and is
required for efficient viral DNA replication (12, 30, 34, 43, 44,
48, 56, 62). A clue to the mechanism of ICP27 action was provided
by Sandri-Goldin and Mendoza (53), who showed that ICP27
enhances expression of constructs bearing a synthetic and incomplete
polyadenylation signal and inhibits expression of reporter genes
bearing certain introns in transient-cotransfection assays. A
complementary series of studies by Clements and colleagues demonstrated
that HSV infection alters the specificity of the host polyadenylation
machinery in an ICP27-dependent fashion, thereby allowing more
efficient use of a subset of viral polyadenylation signals
(31-33). These findings indicate that ICP27 modulates
intranuclear processing of pre-mRNAs and suggest that it inhibits
splicing of at least some intron-bearing transcripts (53).
The hypothesis that ICP27 impairs RNA splicing has been supported by a
considerable amount of data showing the following: (i) unspliced
pre-RNA derived from the intron-bearing HSV genes encoding ICP0 and
UL15 accumulate in the nuclei of some cell types infected with
wild-type HSV but not with an ICP27 mutant (20, 21, 40),
(ii) ICP27 colocalizes with and redistributes snRNPs in HSV-infected
cell nuclei (38), (iii) ICP27 coimmunoprecipitates with
splicing factors that react with anti-Sm antisera and appears to alter
the phosphorylation status of some of these proteins (52),
and (iv) nuclear extracts prepared from cells infected with wild-type
HSV carry out in vitro splicing reactions less efficiently than those
prepared from uninfected cells, and this reduction requires ICP27
(21). The majority of HSV genes lack introns, and therefore,
as originally proposed by Sandri-Goldin and Mendoza (53),
impairment of splicing by ICP27 could contribute to the selective
expression of HSV genes by blocking the processing of most host
pre-mRNAs. Consistent with this view, ICP27 mutants are defective in
delayed shutoff of host cell protein synthesis (20, 48) and
fail to induce the decline in the levels of cellular mRNAs observed
during infection with wild-type HSV (20, 21).
ICP27 binds RNA through an RGG box (36) and shuttles between
the nucleus and cytoplasm of infected cells (35, 39, 50, 58). Recent studies suggest that ICP27 stimulates the cytoplasmic accumulation of intron-less viral mRNAs by binding to these transcripts and mediating their nuclear export (50, 58). The shuttling and RNA export activities of ICP27 depend on a leucine-rich nuclear export sequence that is similar to that of human immunodeficiency virus
(HIV) Rev (50). It is not yet clear how the nuclear export activity of ICP27 relates to its previously described effects on the
intranuclear processing of viral and cellular pre-mRNAs.
We previously reported that the endogenous chromosomal human HSV-1 infection induces multiple
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Herpes Simplex Virus ICP27 Induces Cytoplasmic
Accumulation of Unspliced Polyadenylated
-Globin Pre-mRNA in
Infected HeLa Cells
ABSTRACT
Top
Abstract
Text
References
-globin RNAs in infected HeLa cells. Accumulation of
the unspliced RNA required the immediate-early protein ICP27, and ICP27
was sufficient (in combination with ICP4) to produce this effect in a
transient-transfection assay. However, expression of ICP27 did not
markedly alter the levels of fully spliced -globin transcripts in
infected cells. These data demonstrate that the previously documented
effects of ICP27 on the cellular splicing apparatus do not greatly
inhibit splicing of -globin RNA and argue that ICP27 induces a
splicing-independent pathway for -globin RNA accumulation and
nuclear export.
TEXT
Top
Abstract
Text
References
-globin
gene is activated during HSV infection of HeLa cells, leading to
accumulation of correctly initiated -globin RNAs (6). Analysis of viral mutants demonstrated that the IE proteins ICP0, ICP4,
and ICP22 are each required for efficient induction. The -globin
gene contains two introns, and thus its transcript is a candidate for
ICP27-mediated alterations in splicing. Indeed, since -globin gene
expression stringently requires the IE viral transactivators and is
temporally regulated as a viral E gene (6), the effects of
ICP27 on -globin transcript processing could be highly relevant to
both cellular and viral gene expression during HSV infection. A
substantial amount of evidence has shown that intron-bearing genes
require splicing for the efficient accumulation, polyadenylation, and
nuclear export of their transcripts (1, 7-9, 19, 22, 23, 25, 27,
37, 47). In view of ICP27's putative role in inhibiting mRNA
splicing, one might expect ICP27-deficient mutants to induce
significantly higher levels of -globin RNA than does wild-type HSV.
However, we found that deletion of ICP27 had little effect on the
accumulation of -globin RNA (6). These considerations
prompted us to study the splicing, polyadenylation, and subcellular
location of the -globin transcripts induced by HSV infection.
-globin transcripts in HeLa
cells.
We used Northern blot analysis to examine the number and
sizes of the -globin transcripts present in HSV-1-infected HeLa cells. HeLa cells were infected with HSV-1 strain KOS at an input multiplicity of 10 in the presence of 300 µg of phosphonoacetic acid
(PAA) per ml, and total RNA was extracted 6 h postinfection. PAA
was included to block the reduction of globin RNA levels that otherwise
occurs after the onset of viral DNA replication (6). Total
RNA was also harvested from HeLa cells that were transfected with an
ICP4 expression clone (pBB37) to induce expression of the endogenous
-globin genes or a plasmid bearing the 2-globin gene (pUC2).
pBB37 and pUC2 have been previously described (6). Infection, transfection, and RNA extractions were done as previously described (6). RNA samples were analyzed by electrophoresis on a 1.5% agarose-formaldehyde gel, followed by Northern blot hybridization using a 1.5-kb PstI fragment bearing the human
2-globin gene as a probe. As shown in Fig.
1 (no RNase H), at least two diffuse
bands of -globin RNA were detected in HSV-infected HeLa cells. In
contrast, -globin RNA induced from the endogenous chromosomal 1-and 2-globin genes following transfection of the ICP4
expression vector (pBB37) migrated as a single band, as did the
-globin RNA expressed from the transfected human 2-globin gene
(pUC2). These data show that HSV-1 infection induces the
accumulation of multiple -globin RNA species and that one or more
viral gene products in addition to ICP4 are required to produce this
multiplicity of transcripts.
View larger version (50K):
[in a new window]
FIG. 1.
HSV-1 infection induces multiple -globin RNA species
in HeLa cells. Total RNA was harvested from HeLa cells that were either
mock infected, infected with HSV-1 strain KOS, or transfected with an
ICP4 expression clone (pBB37) or a plasmid bearing the 2-globin gene
(pUC2). The RNA samples were either treated with RNase H in the
presence of oligo(dT) (+RNase H + oligo dT) or left untreated (no
RNase H). The -globin RNA species were examined by Northern blot
analysis using a 1.5-kb PstI fragment bearing the human
2-globin gene as a probe. C, control blood RNA; M, RNA size markers
(in kilobases).
-globin transcripts
present in HSV-infected HeLa cells initiate at the -globin promoter
and are processed at the globin 3' polyadenylation signal (6). Therefore, the multiple RNA species observed in
infected cells likely arise through differential splicing and/or
variation in the length of the 3' poly(A) tail. To examine these
possibilities in more detail, we removed the poly(A) tails from the
transcripts by treating the RNA samples with RNase H in the presence of
oligo(dT). Ten micrograms of total RNA was hybridized to 300 ng of
oligo(dT) (Pharmacia) in a buffer containing 20 mM Tris (pH 7.5), 10 mM MgCl2, 0.5 mM EDTA, 50 mM NaCl, 1 mM dithiothreitol, and 30 µg of bovine serum albumin per ml at 60°C. RNase H (Promega) was added to a final concentration of 0.025 U/µl, and the samples were
incubated at 30°C for 1 h. The cleavage products were recovered by ethanol precipitation and examined by Northern blot analysis (Fig.
1, + RNase H). Removal of the poly(A) tail resolved the diffuse
-globin bands in KOS-infected cells into three discrete bands of
approximately 580, 700, and 840 nucleotides (nt), with the 700-nt
species being considerably fainter than the other two. These
observations excluded the possibility that the multiple globin RNA
species in infected cells are caused by heterogeneity in the length of
the poly(A) tail and instead suggested that they arise through
differential splicing. Consistent with this hypothesis, the 580-nt band
comigrated with deadenylated globin mRNA from transfected cells and
human blood (Fig. 1, + RNase H; also seen in Fig. 3 and 5 for blood
RNA) and therefore likely corresponds to fully spliced globin mRNA
(predicted size of 576 nt). Moreover, the estimated sizes of the
~700- and ~840-nt species closely correspond to those predicted for
transcripts retaining one (688 or 718 nt) and both introns (835 nt)
(see Fig. 3 for evidence confirming these assignments). The untreated
and RNase H-oligo(dT)-treated transcripts found in infected cells
differed in length by approximately 200 to 250 nt, thus documenting the
length of the poly(A) tails of these RNAs. We noted that the
transcripts present in the transfected cells had shorter poly(A) tails
than those present in infected cells (Fig. 1, compare the most rapidly
migrating abundant band in infected cells with the corresponding
species in transfected cells, no RNase H). The basis for this
difference remains to be precisely defined.
ICP27 induces cytoplasmic accumulation of unspliced -globin
RNA.
In order to determine which HSV-1 IE gene products are
required for the accumulation of multiple -globin transcripts during infection, we examined the -globin transcripts in cells infected with a panel of HSV-1 strains that are each defective in one of the IE
genes. HeLa cells were infected in the presence of PAA with strains
KOS, N38 (61), 5dl1.2 (30), n212
(4), d120 (10), or del22Z
(41) (wild type and defective in ICP47, ICP27, ICP0, ICP4,
and ICP22, respectively), and total RNA was harvested 6 h later.
Northern blot analysis showed identical patterns of -globin RNAs in
cells infected with wild-type strain KOS and strain N38 (ICP47-) (Fig.
2A). As demonstrated previously, the ICP0, ICP4, and ICP22-defective strains are severely compromised in
their ability to accumulate -globin RNA; nevertheless, a long exposure of the Northern blot (Fig. 2B) revealed a pattern similar to
that observed in the KOS-infected cells (although the relative abundance of the larger transcripts was somewhat reduced with d120 and n212). In marked contrast, the
ICP27-deficient mutant 5dl1.2 accumulated only the more rapidly
migrating transcript.
|
-globin transcripts
correspond to unspliced and partially spliced derivatives by probing
total RNase H-oligo(dT)-treated RNA from KOS- or 5dl1.2-infected cells
with oligonucleotides specific for -globin intron 1 (5'-AGGCGGCCTTGACGTTGGTCTTGTC-3') or exon 1 (5'-GAGGGTGGCCTGTGGGTCCGGGCGGGCGAG-3') (Fig. 3A and B). The two more slowly migrating bands
present in KOS-infected cells hybridized to the intron 1 probe (Fig.
3A), while all three transcripts hybridized to the exon 1 probe (Fig.
3B). Taken in combination with the data presented and discussed above,
these data confirm that the most rapidly migrating band corresponds to
fully spliced mRNA while the two more slowly migrating bands correspond
to transcripts retaining one and both introns. Only fully spliced RNA
was observed in cells infected with the ICP27-deficient 5dl1.2 mutant
(Fig. 3B and D). Thus, ICP27 is required for accumulation of the
unspliced polyadenylated -globin RNAs. This observation is, at first
glance, generally consistent with the hypothesis that ICP27 inhibits
splicing of -globin pre-mRNA. However, we noted that cells infected
with the ICP27 mutant and wild-type HSV-1 (KOS) displayed essentially
identical amounts of fully spliced -globin mRNA which accumulated at
comparable rates for at least 12 h (Fig. 3C). Moreover, the
unspliced RNA was substantially less abundant (
50%) than the spliced
transcript at all of the time points examined during infection with KOS
(note that the exon-specific probe used in this experiment provides an
accurate estimate of the relative molar abundance of the spliced and
unspliced RNAs, while the genomic probe used in Fig. 1, 2, 4, and 5
overestimates the abundance of the unspliced RNA, because it contains
both intron and exon sequences). Thus, while these data do not exclude
a small inhibitory effect on splicing, they demonstrate that ICP27 does not greatly interfere with the production of spliced -globin transcripts under our conditions of infection (discussed further below).
|
-globin pre-mRNAs, we prepared nuclear
and cytoplasmic RNA fractions from cells infected with wild-type HSV-1
or an ICP27-null mutant strain. Duplicate dishes of HeLa cells were
infected with HSV-1 strain KOS1.1 or d27-1 (45)
in the presence of PAA. At 6 h postinfection, total RNA was
harvested from one dish by using the RNeasy purification kit (Qiagen).
Cytoplasmic and nuclear RNA fractions were isolated from the second
dish of cells according to the RNeasy handbook (Qiagen). The combined
yields of cytoplasmic and nuclear RNAs equalled that of the total RNA
and represented approximately 60 to 70% and 30 to 40%, respectively,
of the total RNA yield. Cell equivalents of total, nuclear, and
cytoplasmic RNA were treated with RNase H and oligo(dT) and then
analyzed by Northern blot hybridization for the presence of -globin
transcripts (Fig. 4A). Surprisingly, the
majority of the unspliced -globin RNA in cells infected with
wild-type HSV-1 was found in the cytoplasmic fraction. Indeed, the
subcellular distribution of the unspliced RNA could not be
distinguished from that of the spliced transcript. The same RNA samples
were analyzed for their content of the U3 snoRNA, which is exclusively
nuclear, by probing with an oligonucleotide specific for U3
(5'-ACCACTCAGACCGCGTTCTCTCCCTCTCAC-3') (Fig. 4B). As
expected, the U3 snoRNA was located entirely in the nuclear RNA
fraction, indicating that the cytoplasmic fraction was free of nuclear
RNA contamination. These data indicate that HSV infection induces
efficient cytoplasmic accumulation of polyadenylated unspliced -globin RNA, and ICP27 is required for this effect. These findings are in contrast with the reports by others that ICP27 causes nuclear retention of unspliced pre-mRNAs of two intron-containing HSV-1 transcripts, ICP0 and UL15 (40, 50), and demonstrate that nuclear retention of intron-containing transcripts by ICP27 is not
universal.
|
-globin RNA in the absence of HSV
infection. Expression of ICP4 suffices to activate the endogenous
-globin gene in transfected HeLa cells (6). We therefore
cotransfected the ICP4 expression plasmid pBB37 with an ICP27
expression vector, pC27, into HeLa cells. pC27 bears the ICP27 open
reading frame under the control of the TET-OFF promoter of pUHD10-3
(35). Although the TET-OFF promoter is inactive in HeLa
cells (17), ICP27 expression was efficiently induced by
coexpression of ICP4 (data not shown). RNA was extracted 36 h
posttransfection and treated with RNase H and oligo(dT), and the
-globin transcripts were examined by Northern blot analysis (Fig.
5). Only fully spliced globin RNA was
detected in cells expressing ICP4, while addition of ICP27 induced
accumulation of the same unspliced -globin species seen in
HSV-infected cells. Furthermore, as in HSV-infected cells, the majority
of the unspliced -globin pre-mRNA was present in the cytoplasmic RNA
fraction (data not shown). Thus, ICP27 is sufficient (in combination
with ICP4) to induce cytoplasmic accumulation of unspliced
polyadenylated -globin RNA in the absence of other HSV gene
products. We observed a 40% reduction in the total -globin signal
(spliced plus unspliced RNA) in the presence of ICP27, an effect that
was not observed during infection with wild-type versus ICP27-deficient
HSV. It is unlikely that this reflects a reduced splicing efficiency, since if such were the case, one would predict the total -globin signal to be the same but with a decrease of the spliced message and a
corresponding increase in the unspliced transcript. The possibility
that the reduction in -globin message stems from overexpression of
ICP27 in the transfected cells is presently under investigation.
|
-globin
RNA demonstrates that the splicing apparatus retains the ability to
process this transcript for extended periods in HSV-infected cells
maintained in the presence of PAA. In contrast, previous work has shown
that the expression of ICP27 greatly reduces accumulation of spliced
transcripts derived from several other host intron-bearing genes during
infection (20, 21), presumably due to defective splicing,
and this effect is thought to be responsible (at least in part) for the
ICP27-dependent delayed shutoff of host cell protein synthesis. It is
unclear why ICP27 has varied effects on cellular transcripts. One
possibility is that cellular genes vary in their sensitivity to the
ICP27-induced alterations of the splicing apparatus. Perhaps splicing
of the -globin transcript is relatively resistant because -globin
pre-mRNA contains only two small introns, whereas most cellular genes
contain many more introns, and these are on average much larger than
those in the globin gene (see for example reference
18). Alternatively, the effects of ICP27 on the
-globin transcript may differ because, unlike with most other
cellular genes, expression and accumulation of -globin RNA is
actively induced by the actions of viral gene products. Inasmuch as the
-globin gene is in this sense acting as a surrogate viral gene, its
behavior may reflect a global distinction by ICP27 between viral and
cellular transcripts.
Second, we find that the unspliced polyadenylated -globin pre-mRNA
is exported from the nucleus as efficiently as the fully spliced
message. This was a surprising observation because a large amount of
evidence indicates that splicing is required for efficient accumulation, polyadenylation, and nuclear export of transcripts of
intron-bearing genes in metazoan cells. Interestingly, the fully
spliced -globin message efficiently gained access to the cytoplasm
in the absence of ICP27 (Fig. 4A). These data therefore raise the
possibility that two modes exist for nuclear export of -globin
transcripts during HSV infection: the splicing-dependent pathway that
intron-bearing genes normally utilize and an alternative splicing-independent pathway that requires ICP27 for accumulation and
export of unspliced -globin transcripts. In this regard, ICP27 may
be acting analogously to the HIV Rev protein. Rev binds to a specific
cis-acting element (the RRE) present in unspliced and
partially spliced HIV RNAs and promotes nuclear export of these
transcripts (reviewed in reference 42). Several
naturally intronless mRNAs, both viral and cellular, similarly require
specific cis-acting sequences that promote
splicing-independent RNA export (24, 26, 27). For example,
the cellular hnRNP L protein binds to multiple elements in the HSV-TK
transcript that are each able to mediate splicing-independent
cytoplasmic accumulation (27). Recent evidence indicates
that such cis-acting elements suppress the use of cryptic
splice sites and stimulate splicing-independent polyadenylation of
these transcripts, as well as promoting their nuclear export
(25). It is tempting to speculate that ICP27 acts in a
fashion similar to Rev and hnRNP L. Consistent with this view,
Sandri-Goldin (50) has shown that ICP27 binds to several
intron-less HSV transcripts and mediates their splicing-independent RNA
export. However, Sandri-Goldin found that transcripts of the intron-bearing viral ICP0 and UL15 genes did not detectably interact with ICP27 in these assays and were preferentially retained in the
nucleus. These data were interpreted to indicate that ICP27 globally
distinguishes between intron-bearing and intron-less RNAs and
transports only the latter (50). Our findings suggest an
alternative interpretation: perhaps ICP27 recognizes specific features
that are present in only a subset of RNAs and transports these
transcripts irrespective of the presence or absence of introns. Supporting this hypothesis are the recent data of Buisson et al. (2). These authors showed that the Epstein-Barr virus (EBV) homologue of ICP27, EB2, induces the cytoplasmic accumulation of
unspliced RNA derived from some genes bearing constitutive splicing
signals without reducing accumulation of spliced RNA. Interestingly,
the EB2 protein also blocked the use of cryptic (noncanonical) splicing
signals in transcripts lacking bona fide introns, thereby promoting
cytoplasmic accumulation of unspliced transcripts of these intron-less genes.
Intron-containing transcripts are normally recognized by splicing
factors and assembled into spliceosomes. The protein-bound pre-mRNA is
then either productively spliced into mRNA or degraded by as yet poorly
understood discard pathways (3, 28). In some cases, a
substantial fraction of the intron-containing nuclear pre-mRNA is
degraded rather than spliced (28). One interpretation of our
data is that ICP27 rescues this subset of nuclear -globin RNA from
degradation, for example, by dissociating it from nonproductive interactions with the splicing machinery and promoting its
polyadenylation and nuclear export. According to this view, the
unspliced globin RNAs that accumulate in the presence of ICP27 derive
from a subset of primary transcripts that would have been degraded in
its absence. The proposed mechanism is again reminiscent of that used
by the HIV Rev protein, which increases the intranuclear stability of unspliced HIV RNA as well as facilitates its export to the cytoplasm (11, 14, 28, 29, 54). Alternatively, ICP27 may intercept a
fraction of globin pre-mRNAs before they engage the splicing apparatus
and mediate their efficient polyadenylation and transport.
It seems possible that ICP27-induced cytoplasmic accumulation of
unspliced transcripts plays a biological role during HSV infections.
Phelan et al. (40) and Hardy and Sandri-Goldin
(21) have shown that a fraction of the unspliced ICP0 and
UL15 RNA is present in the cytoplasm, and Everett et al. obtained
direct evidence that truncated forms of ICP0 are translated from
partially unspliced ICP0 transcripts that retain intron 2 (13). More generally, it is interesting to speculate that
the proposed "transcript rescue" function of ICP27 plays a
fundamental role in HSV gene expression. Splicing signals are highly
degenerate, and cryptic splice donor and acceptor signals are therefore
likely to appear by chance in HSV transcripts that lack efficient or
bona fide introns. Although insufficient for splicing, such signals are
predicted to promote nonproductive interactions with the splicing
machinery, leading to nuclear retention (5) or degradation
through the discard pathway. The proposed rescue function would serve
to counteract this effect. This proposal is consistent with the
observation that EBV EB2 rescues transcripts bearing weak splicing
signals (2). Intriguingly, a small fraction of HSV
glycoprotein C mRNA is spliced, indicating the presence of weak
splicing signals in this transcript (15). The gC protein is
translated from the unspliced form of the RNA. It is therefore perhaps
significant that accumulation of unspliced gC mRNA stringently requires
ICP27 (44).
The hypothesis that ICP27 stimulates accumulation of unspliced
-globin mRNA by inducing a splicing-independent pathway for globin
RNA accumulation and nuclear export predicts that accumulation of
unspliced -globin pre-mRNA could be uncoupled by mutation from the
previously described intron-dependent "repression" function of
ICP27. Experiments designed to test this prediction are under way.
| |
ACKNOWLEDGMENTS |
|---|
P.C. and K.S.E. contributed equally to this work.
We thank Joanne Duncan, Carol Lavery, Holly Saffran, and Rob Maranchuk for superb technical assistance, Peter O'Hare for pBB37, and Steve Rice for pC27, stimulating discussions, and a critical review of an earlier version of the manuscript.
This research was supported by a grant from the Medical Research Council of Canada (MT-12172). P.C. held a studentship from the MRC, and J.R.S. was a Terry Fox Senior Scientist of the National Cancer Institute of Canada.
| |
FOOTNOTES |
|---|
* Corresponding author. Mailing address: Department of Medical Microbiology & Immunology, 1-41, Medical Sciences Bldg., University of Alberta, Edmonton, Alberta T6G 2H7, Canada. Phone: (780) 492-2308. Fax: (780) 492-7521. E-mail: jim.smiley{at}ualberta.ca.
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REFERENCES |
|---|
|
Top
Abstract
Text
References
|
|---|
| 1. |
Buchman, A. R., and P. Berg.
1988.
Comparison of intron-dependent and intron-independent gene expression.
Mol. Cell. Biol.
8:4395-4405 |
| 2. |
Buisson, M.,
F. Hans,
I. Kusters,
N. Duran, and A. Sergeant.
1999.
The C-terminal region but not the Arg-X-Pro repeat of Epstein-Barr virus protein EB2 is required for its effect on RNA splicing and transport.
J. Virol.
73:4090-4100 |
| 3. | Burgess, S. M., and C. Guthrie. 1993. A mechanism to enhance mRNA splicing fidelity: the RNA-dependent ATPase Prp16 governs usage of a discard pathway for aberrant lariat intermediates. Cell 73:1377-1391[CrossRef][Medline]. |
| 4. | Cai, W., and P. A. Schaffer. 1989. Herpes simplex virus type 1 ICP0 plays a critical role in the de novo synthesis of infectious virus following transfection of viral DNA. J. Virol. 63:4570-4589. |
| 5. | Chang, D. D., and P. A. Sharp. 1989. Regulation by HIV Rev depends upon recognition of splice sites. Cell 59:789-795[CrossRef][Medline]. |
| 6. |
Cheung, P.,
B. Panning, and J. R. Smiley.
1997.
Herpes simplex virus immediate-early proteins ICP0 and ICP4 activate the endogenous human -globin gene in nonerythroid cells.
J. Virol.
71:1748-1793.
|
| 7. |
Chiou, H. C.,
C. Dabrowski, and J. C. Alwine.
1991.
Simian virus 40 late mRNA leader sequences involved in augmenting mRNA accumulation via multiple mechanisms, including increased polyadenylation efficiency.
J. Virol.
65:6677-6685 |
| 8. | Cooke, C., and J. C. Alwine. 1996. The cap and the 3' splice site similarly affect polyadenylation efficiency. Mol. Cell. Biol. 16:2579-2584[Abstract]. |
| 9. |
Cooke, C.,
H. Hans, and J. C. Alwine.
1999.
Utilization of splicing elements and polyadenylation signal elements in the coupling of polyadenylation and last-intron removal.
Mol. Cell. Biol.
19:4971-4979 |
| 10. |
DeLuca, N. A.,
A. M. McCarthy, and P. A. Schaffer.
1985.
Isolation and characterization of deletion mutants of herpes simplex virus type 1 in the gene encoding immediate-early regulatory protein ICP4.
J. Virol.
56:558-570 |
| 11. | Emerman, M., R. Vazeux, and K. Peden. 1989. The rev gene product of the human immunodeficiency virus affects envelope-specific RNA localization. Cell 57:1155-1165[CrossRef][Medline]. |
| 12. |
Everett, R. D.
1986.
The products of herpes simplex virus type 1 (HSV-1) immediate early genes 1, 2, and 3 can activate HSV-1 gene expression in trans.
J. Gen. Virol.
67:2507-2513 |
| 13. | Everett, R. D., A. Cross, and A. Orr. 1993. A truncated form of herpes simplex virus type 1 immediate-early protein Vmw110 is expressed in a cell type dependent manner. Virology 197:751-756[CrossRef][Medline]. |
| 14. |
Febler, B. K.,
M. Hadzopoulou-Cladaras,
C. Cladaras,
T. Copeland, and G. N. Pavlakis.
1989.
Rev protein of human immunodeficiency virus type 1 affects the stability and transport of the viral mRNA.
Proc. Natl. Acad. Sci. USA
86:1495-1499 |
| 15. |
Frink, R. J.,
R. Eisenberg,
G. Cohen, and E. K. Wagner.
1983.
Detailed analysis of the portion of the herpes simplex virus type 1 genome encoding glycoprotein C.
J. Virol.
45:634-647 |
| 16. | Goding, C. R., and P. O'Hare. 1989. Herpes simplex virus Vmw65-octamer binding protein interaction: a paradigm for combinatorial control of transcription. Virology 173:363-367[CrossRef][Medline]. |
| 17. |
Gossen, M., and H. Bujard.
1992.
Tight control of gene expression in mammalian cells by tetracycline-responsive promoters.
Proc. Natl. Acad. Sci. USA
89:5547-5551 |
| 18. | Haig, D. 1996. Do imprinted genes have few and small introns? Bioessays 18:351-353[CrossRef][Medline]. |
| 19. | Hamer, D. H., and P. Leder. 1979. Splicing and the formation of stable RNA. Cell 18:1299-1302[CrossRef][Medline]. |
| 20. |
Hardwicke, M. A., and R. M. Sandri-Goldin.
1994.
The herpes simplex virus regulatory protein ICP27 contributes to the decrease in cellular mRNA levels during infection.
J. Virol.
68:4797-4810 |
| 21. |
Hardy, W. R., and R. M. Sandri-Goldin.
1994.
Herpes simplex virus inhibits host cell splicing, and regulatory protein ICP27 is required for this effect.
J. Virol.
68:7790-7799 |
| 22. | Hentschel, C. C., and M. L. Birnstiel. 1981. The organization and expression of histone gene families. Cell 25:301-313[CrossRef][Medline]. |
| 23. | Huang, Y., and G. G. Carmichael. 1996. Role of polyadenylation in nucleocytoplasmic transport of mRNA. Mol. Cell. Biol. 16:1534-1542[Abstract]. |
| 24. |
Huang, Y., and G. G. Carmichael.
1997.
The mouse histone H2a gene contains a small element that facilitates cytoplasmic accumulation of intronless gene transcripts and of unspliced HIV-1-related mRNAs.
Proc. Natl. Acad. Sci. USA
94:10104-10109 |
| 25. | Huang, Y., K. M. Wimler, and G. G. Carmichael. 1999. Intronless mRNA transport elements may affect multiple steps of pre-mRNA processing. EMBO J. 18:1642-1652[CrossRef][Medline]. |
| 26. | Huang, Z. M., and T. S. Yen. 1995. Role of the hepatitis B virus posttranscriptional regulatory element in export of intronless transcripts. Mol. Cell. Biol. 15:3864-3869[Abstract]. |
| 27. |
Liu, X., and J. E. Mertz.
1995.
HnRNP L binds a cis-acting RNA sequence element that enables intron-dependent gene expression.
Genes Dev.
9:1766-1780 |
| 28. |
Malim, M. H., and B. R. Cullen.
1993.
Rev and the fate of pre-mRNA in the nucleus: implications for the regulation of RNA processing in eukaryotes.
Mol. Cell. Biol.
13:6180-6189 |
| 29. | Malim, M. H., J. Hauber, S.-Y. Le, J. V. Maizel, and B. R. Cullen. 1989. The HIV-1 rev trans-activator acts through a structured target sequence to activate nuclear export of unspliced viral mRNA. Nature 338:254-257[CrossRef][Medline]. |
| 30. |
McCarthy, A. M.,
L. McMahan, and P. A. Schaffer.
1989.
Herpes simplex virus type 1 ICP27 deletion mutant exhibits altered patterns of transcription and are DNA deficient.
J. Virol.
63:18-27 |
| 31. | McGregor, F., A. Phelan, J. Dunlop, and J. B. Clements. 1996. Regulation of herpes simplex virus poly(A) site usage and the action of immediate-early protein IE63 in the early-late switch. J. Virol. 70:1931-1940[Abstract]. |
| 32. |
McLauchlan, J.,
P. C. Loney,
R. M. Sandri-Goldin, and J. B. Clements.
1992.
Herpes simplex virus IE63 acts at the posttranscriptional level to stimulate viral mRNA 3' processing.
J. Virol.
66:6939-6945 |
| 33. | McLauchlan, J., S. Simpson, and J. B. Clements. 1989. Herpes simplex virus induces a processing factor that stimulates poly(A) site usage. Cell 59:1093-1105[CrossRef][Medline]. |
| 34. |
McMahan, L., and P. A. Schaffer.
1990.
The repressing and enhancing functions of the herpes simplex virus regulatory protein ICP27 map to the C-terminal regions and are required to modulate viral gene expression very early in infection.
J. Virol.
64:3471-3485 |
| 35. | Mears, W. E., and S. A. Rice. 1998. The herpes simplex virus immediate-early protein ICP27 shuttles between nucleus and cytoplasm. Virology 242:128-137[CrossRef][Medline]. |
| 36. | Mears, W. E., and S. A. Rice. 1996. The RGG box motif of the herpes simplex virus ICP27 protein mediates an RNA-binding activity and determines in vivo methylation. J. Virol. 70:7445-7453[Abstract]. |
| 37. |
Niwa, M.,
S. D. Rose, and S. M. Berget.
1990.
In vitro polyadenylation is stimulated by the presence of an upstream intron.
Genes Dev.
4:1552-1559 |
| 38. |
Phelan, A.,
M. Carmo-Fonseca,
J. McLauchlan,
A. I. Lamond, and J. B. Clements.
1993.
A herpes simplex virus type-1 immediate early gene product IE63 regulates small ribonucleoprotein distribution.
Proc. Natl. Acad. Sci. USA
90:9056-9060 |
| 39. | Phelan, A., and J. B. Clements. 1997. Herpes simplex virus type 1 immediate early protein IE63 shuttles between nuclear compartments and the cytoplasm. J. Gen. Virol. 78:3327-3331[Abstract]. |
| 40. |
Phelan, A.,
J. Dunlop, and J. B. Clements.
1996.
Herpes simplex virus type 1 protein IE63 affects the nuclear export of virus intron-containing transcripts.
J. Virol.
70:5255-5265 |
| 41. | Poffenberger, K. L., P. E. Raichlen, and R. C. Herman. 1993. In vitro characterization of a herpes simplex virus type 1 ICP22 deletion mutant. Virus Genes 7:171-186[CrossRef][Medline]. |
| 42. | Pollard, V. W., and M. H. Malim. 1998. The HIV-1 Rev protein. Annu. Rev. Microbiol. 52:491-532[CrossRef][Medline]. |
| 43. |
Rice, S. A., and D. M. Knipe.
1988.
Gene-specific transactivation by herpes simplex virus type 1 alpha protein ICP27.
J. Virol.
62:3814-3823 |
| 44. |
Rice, S. A., and D. M. Knipe.
1990.
Genetic evidence for two distinct trans-activation functions of the herpes simplex virus protein ICP27.
J. Virol.
64:1704-1715 |
| 45. |
Rice, S. A., and V. Lam.
1994.
Amino acid substitution mutations in the herpes simplex virus ICP27 protein define an essential gene regulation function.
J. Virol.
68:823-833 |
| 46. | Roizman, B., and A. E. Sears. 1996. Herpes simplex viruses and their replication, p. 2231-2295. In B. N. Fields, D. M. Knipe, and P. M. Howley (ed.), Fields virology, 3rd ed. Lippincott-Raven, Philadelphia, Pa. |
| 47. |
Ryu, W. S., and J. E. Mertz.
1989.
Simian virus 40 late transcripts lacking excisable intervening sequences are defective in both stability in the nucleus and transport to the cytoplasm.
J. Virol.
63:4386-4394 |
| 48. |
Sacks, W. R.,
C. C. Greene,
D. P. Ashman, and P. A. Schaffer.
1985.
Herpes simplex virus type 1 ICP27 is an essential regulatory protein.
J. Virol.
55:796-805 |
| 49. |
Sacks, W. R., and P. A. Schaffer.
1987.
Deletion mutants in the gene encoding the herpes simplex virus type 1 immediate-early protein ICP0 exhibit impaired growth in cell culture.
J. Virol.
61:829-839 |
| 50. |
Sandri-Goldin, R. M.
1998.
ICP27 mediates HSV RNA export by shuttling through a leucine-rich nuclear export signal and binding viral intronless RNAs through an RGG motif.
Genes Dev.
12:868-879 |
| 51. | Sandri-Goldin, R. M. 1998. Interactions between a herpes simplex virus regulatory protein and cellular mRNA processing pathways. Methods 16:95-104[CrossRef][Medline]. |
| 52. | Sandri-Goldin, R. M., and M. K. Hibbard. 1996. The herpes simplex virus type 1 regulatory protein ICP27 coimmunoprecipitates with anti-sm antiserum, and the C terminus appears to be required for this interaction. J. Virol. 70:108-118[Abstract]. |
| 53. |
Sandri-Goldin, R. M., and G. E. Mendoza.
1992.
A herpesvirus regulatory protein appears to act post-transcriptionally by affecting mRNA processing.
Genes Dev.
6:848-863 |
| 54. |
Schwartz, S.,
B. K. Felber, and G. N. Pavlakis.
1992.
Distinct RNA sequences in the gag region of human immunodeficiency virus type 1 decrease RNA stability and inhibit expression in the absence of Rev protein.
J. Virol.
66:150-160 |
| 55. |
Sears, A. E.,
I. W. Halliburton,
B. Meignier,
S. Silver, and B. Roizman.
1985.
Herpes simplex virus 1 mutant deleted in the alpha-22 gene: growth and gene expression in permissive and restrictive cells and establishment of latency in mice.
J. Virol.
55:338-346 |
| 56. |
Sekulovich, R. E.,
K. Leary, and R. M. Sandri-Goldin.
1988.
The herpes simplex virus type 1 protein ICP27 can act as a trans-repressor or a trans-activator in combination with ICP4 and ICP0.
J. Virol.
62:4510-4522 |
| 57. | Smith, I. L., M. A. Hardwicke, and R. M. Sandri-Goldin. 1992. Evidence that the herpes simplex virus immediate early protein ICP27 acts post-transcriptionally during infection to regulate gene expression. Virology 186:74-86[CrossRef][Medline]. |
| 58. | Soliman, T. M., R. M. Sandri-Goldin, and S. J. Silverstein. 1997. Shuttling of the herpes simplex virus type 1 regulatory protein ICP27 between the nucleus and cytoplasm mediates the expression of late proteins. J. Virol. 71:9188-9197[Abstract]. |
| 59. |
Stow, N. D., and E. C. Stow.
1986.
Isolation and characterization of a herpes simplex virus type 1 mutant containing a deletion within the gene encoding the immediate early polypeptide Vmw110.
J. Gen. Virol.
67:2571-2585 |
| 60. | Thompson, C. C., and S. L. McKnight. 1992. Anatomy of an enhancer. Trends Genet. 8:232-236. |
| 61. |
Umene, K.
1986.
Conversion of a fraction of the unique sequences to part of the inverted repeats in the S component of the herpes simplex virus type 1 genome.
J. Gen. Virol.
67:1035-1048 |
| 62. | Uprichard, S. L., and D. M. Knipe. 1996. Herpes simplex ICP27 mutant viruses exhibit reduced expression of specific DNA replication genes. J. Virol. 70:1969-1980[Abstract]. |
| 63. | Watson, R. J., and J. B. Clements. 1980. A herpes simplex virus type 1 function continuously required for early and late virus RNA synthesis. Nature 285:329-330[CrossRef][Medline]. |
| 64. | Weinheimer, S. P., and S. L. McKnight. 1987. Transcriptional and post-transcriptional controls establish the cascade of herpes simplex virus protein synthesis. J. Mol. Biol. 195:819-833[CrossRef][Medline]. |
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