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Journal of Virology, March 2000, p. 2107-2120, Vol. 74, No. 5
Department of Microbiology, University of
Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6076
Received 22 September 1999/Accepted 3 December 1999
We have previously shown that two inhibitors specific for cellular
cyclin-dependent kinases (cdks), Roscovitine (Rosco) and Olomoucine
(Olo), block the replication of herpes simplex virus (HSV). Based on
these results, we demonstrated that HSV replication requires cellular
cdks that are sensitive to these drugs (L. M. Schang, J. Phillips,
and P. A. Schaffer. J. Virol. 72:5626-5637, 1998). We
further established that at least two distinct steps in the viral
replication cycle require cdks: transcription of immediate-early (IE)
genes and transcription of early (E) genes (L. M. Schang, A. Rosenberg, and P. A. Schaffer, J. Virol. 73:2161-2172, 1999). Since Rosco inhibits HSV replication efficiently even when added
to infected cells at 6 h postinfection, we postulated that cdks
may also be required for viral functions that occur after E gene
expression. In the study presented herein, we tested this hypothesis
directly by measuring the efficiency of viral replication, viral DNA
synthesis, and expression of several viral genes during infections in
which Rosco was added after E proteins had already been synthesized.
Rosco inhibited HSV replication, and specifically viral DNA synthesis,
when the drug was added at the time of release from a 12-h
phosphonoacetic acid (PAA)-induced block in viral DNA synthesis.
Inhibition of DNA synthesis was not a consequence of inhibition of
expression of IE or E genes in that Rosco had no effect on steady-state
levels of two E transcripts under the same conditions in which it
inhibited viral DNA synthesis. Moreover, viral DNA synthesis was
inhibited by Rosco even in the absence of protein synthesis. In a
second series of experiments, the replication of four HSV mutants
harboring temperature-sensitive mutations in genes essential for viral
DNA replication was inhibited when Rosco was added at the time of
shift-down from the nonpermissive to the permissive temperature. Viral
DNA synthesis was inhibited by Rosco under these conditions, whereas
expression of viral E genes was not affected. We conclude that cellular
Rosco-sensitive cdks are required for replication of viral DNA in the
presence of viral E proteins. This requirement may indicate that HSV
DNA synthesis is functionally linked to transcription, which requires cdks, or that both viral transcription and DNA replication,
independently, require viral or cellular factors activated by
Rosco-sensitive cdks.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Roscovitine, a Specific Inhibitor of Cellular
Cyclin-Dependent Kinases, Inhibits Herpes Simplex Virus DNA Synthesis
in the Presence of Viral Early Proteins
*
Corresponding author. Mailing address: Department of
Microbiology, University of Pennsylvania School of Medicine, 3610 Hamilton Walk, Philadelphia, PA 19104-6076. Phone: (215) 573-9863. Fax: (215) 573-5344. E-mail: pschfr{at}mail.med.upenn.edu.
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