Previous Article | Next Article ![]()
J. Virol., Nov 1996, 7433-7444, Vol 70, No. 11
DP Frazier, D Cox, EM Godshalk and PA Schaffer
In the absence of detectable viral proteins, expression of the latency-
associated transcripts (LATs) is likely regulated by cellular factors
during latent infection of neurons with herpes simplex virus type 1. The
amounts and activation states of these factors may in turn be regulated by
extracellular regulatory factors. Consistent with this hypothesis, we have
recently demonstrated that LAT expression is significantly enhanced by
nerve growth factor (NGF) and sodium butyrate (NaB) in neurally derived
PC12 cells. With the ultimate goal of identifying trans-acting cellular
factors involved in regulating LAT expression during latency, we have
attempted to identify the cis-acting elements to which these putative
cellular factors bind by characterizing the LAT promoter and a series of 5'
promoter deletion mutants in PC12 cells following treatment with the
LAT-enhancing agents NGF and NaB. Transient expression assays demonstrated
that distinct cis- acting sequences mediate basal and induced LAT promoter
expression. Basal activity in PC12 cells is mediated by two elements: a
negative regulatory element between -435 and -270 and a positive element
between -240 and -204. The positive element contains binding sites for the
transactivator Sp-1, whereas the negative element bears some resemblance to
known neuron-specific silencer elements. In contrast to basal expression,
maximum induction of the LAT promoter by NGF and NaB requires sequences
between -159 and -81. Using gel mobility shift assays, we have identified
three sets of protein-DNA complexes that bind to this 78-bp region and
shown by competition analysis that binding is specific. The abundance and
mobility of these complexes were altered by treatment with NGF or NaB. The
nucleotide sequences to which these complexes bind were fine mapped by
competition analysis with oligonucleotide probes containing substitution
mutations. The target sequences identified exhibit no homology to binding
sites of known transcription factors. These regions were critical for
complex formation in vitro and for maximum induction of the LAT promoter by
NGF and NaB in transient expression assays. The protein complexes that form
with target sequences likely participate in the regulation of LAT
expression in response to physiological stimuli in neurons in vivo.
Copyright © 1996, American Society for Microbiology
Identification of cis-acting sequences in the promoter of the herpes simplex virus type 1 latency-associated transcripts required for activation by nerve growth factor and sodium butyrate in PC12 cells
Division of Molecular Genetics, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
This article has been cited by other articles:
| J. Bacteriol. | Mol. Cell. Biol. | Microbiol. Mol. Biol. Rev. |
|---|
| Clin. Vaccine Immunol. | ALL ASM JOURNALS |
|---|