Herpes simplex virus 1 activates cdc2 to recruit topoisomerase IIα for post-DNA synthesis expression of late genes

Abstract

A subset (␥2) of late herpes simplex virus 1 genes depends on viral DNA synthesis for its expression. For optimal expression, a small number of these genes, exemplified by U S11, also requires two viral proteins, the ␣ protein infected cell protein (ICP) 22 and the protein kinase U L13. Earlier we showed that UL13 and ICP22 mediate the stabilization of cdc2 and the replacement of its cellular partner, cyclin B, with the viral DNA polymerase processivity factor U L42. Here we report that cdc2 and its new partner, UL42, bind a phosphorylated form of topoisomerase II␣. The posttranslational modification of topoisomerase II␣ and its interaction with cdc2-UL42 proteins depend on ICP22 in infected cells. Although topoisomerase II is required for viral DNA synthesis, ICP22 is not, indicating a second function for topoisomerase II␣. The intricate manner in which the virus recruits topoisomerase II␣ for post-DNA synthesis expression of viral genes suggests that topoisomerase II␣ also is required for untangling concatemeric DNA progeny for optimal transcription of late genes.H erpes simplex virus 1 (HSV-1) encodes at least 84 unique ORFs. Its genes are expressed in a coordinately regulated, sequentially ordered manner (1, 2). ␣ genes are expressed first, and their products enable the expression of ␤ (early) and ␥ (late) genes. The latter genes are classified further as ␥ 1 or ␥ 2 genes. Whereas ␥ 2 gene expression requires viral DNA synthesis, the expression of ␥ 1 is enhanced by but is not totally dependent on viral DNA synthesis. Studies have shown that primary human cell strains and some animal cell lines accumulate grossly reduced amounts of a subset of ␥ 2 proteins exemplified by the products of U S 11, U L 38, or U L 41 after infection with mutants lacking the genes encoding infected cell protein (ICP) 22 or the U L 13 protein kinase (3, 4). An apparent involvement of cellular factors in the expression of this subset of viral genes emerged from studies of cell cycle proteins. In these studies it was noted that the cyclin-dependent kinase cdc2 (cdk1) was posttranslationally modified, stabilized, and activated 4-12 h after infection (5). Concurrently, cyclin B, a partner of cdc2, was degraded. Mapping studies with viral mutants revealed that both the posttranslational modification of cdc2 and the degradation of cyclin B depended on the presence of ICP22 and U L 13 protein kinase. Further studies reinforced the apparent connection between the phenotype of mutant viruses from which either ␣22 or U L 13 mutants were deleted and the activation of cdc2 in infected cells. Thus cells transfected with a dominant negative (dn) mutant of cdc2 and infected with wild-type virus expressed representative ␣, ␤, and ␥ 1 proteins but failed to express the ␥ 2 U S 11 protein (6). These studies linked the stabilization of cdc2 with the expression of the U S 11 gene and indicated that ICP22 and U L 13 mediate the accumulation of the subset of ␥ 2 proteins represented by U S 11 by inducing the posttranslational modification of cdc2, but t...

Ionizing Radiation Activates Late Herpes Simplex Virus 1 Promoters via the p38 Pathway in Tumors Treated with Oncolytic Viruses

“…In recent studies, it has been shown that the expression of glycoprotein C and U S 11 is enhanced by the ICP22-mediated interaction of the viral DNA processivity factor U L 42 (a viral functional homologue of proliferating cell nuclear antigen), cyclin-dependent kinase cdc2, and topoisomerase IIa (34)(35)(36). One hypothesis that could explain the mechanism of activation of late promoters and the role of ionizing radiation in inducing these promoters is that these are activated by modifications in the structure of the DNA, either as a result of nicks, gaps, or other perturbations in the DNA structure.…”

Role of cdk9 in the Optimization of Expression of the Genes Regulated by ICP22 of Herpes Simplex Virus 1

“…A key function expressed by the carboxyl-terminal domain (CTD) of ICP22 in conjunction with the viral U L 13 protein kinase is to enhance the synthesis of a subset of late (␥ 2 ) proteins exemplified by the products of the U L 38, U L 41, and U S 11 genes (2,24,31,37). In earlier studies, this laboratory reported that ICP22 and the U L 13 protein kinase mediate the activation of cdc2 and degradation of its partners, cyclins A and B (3,4). cdc2 and its new partner, the viral DNA polymerase accessory factor (U L 42), bind topoisomerase II␣ in an ICP22-dependent manner (1,4).…”

“…In earlier studies, this laboratory reported that ICP22 and the U L 13 protein kinase mediate the activation of cdc2 and degradation of its partners, cyclins A and B (3,4). cdc2 and its new partner, the viral DNA polymerase accessory factor (U L 42), bind topoisomerase II␣ in an ICP22-dependent manner (1,4). In addition, ICP22 and U L 13 mediate an intermediate phosphorylation of the carboxyl terminus of RNA polymerase II (Pol II) in Vero cells (14,18,34,35).…”

Human Cytomegalovirus Tegument Protein pp71 Directs Long-Term Gene Expression from Quiescent Herpes Simplex Virus Genomes

“…However, the experiments also raise the possibility that the action of pp71 is indirect. The HSV-1 IE proteins ICP22 and ICP27, encoded by US1 and UL54, respectively, have each been implicated in transcriptional regulation (1,34,58,63,64); thus, it could be these proteins that mediated the long-term expression, either alone or in combination with pp71. To resolve whether this was the case, derivatives of in1312 with an additional deletion of US1 or UL54 were constructed.…”