Oct-1 Is Posttranslationally Modified and Exhibits Reduced Capacity To Bind Cognate Sites at Late Times after Infection with Herpes Simplex Virus 1

Abstract

ABSTRACT In herpes simplex virus 1-infected cells, a high level of α gene expression requires the transactivation of the genes by a complex containing the viral α transinducing factor (αTIF) and two cellular proteins. The latter two, HCF-1 and octamer binding protein Oct-1, are transcriptional factors regulated in a cell cycle-dependent manner. αTIF is a protein made late in infection but packaged with the virion to transactivate viral genes in newly infected cells. In light of the accumulation of large amounts of αTIF, the absence of α gene expression late in infection suggested the possibility that one or more transcriptional factors required for α gene expression is modified late in infection. Here we report that Oct-1 is posttranscriptionally modified late in infection, that the modification is mediated by the virus but does not involve viral protein kinases or cdc2 kinase activated by the virus late in infection, and that the modified Oct-1 has a reduced affinity for its cognate DNA site. These results are consistent with the hypothesis that modification of Oct-1 transcriptional factor could account at least in part for the shutoff of α gene expression late in infection.