During lytic infection, herpes simplex virus type 1 (HSV-1) represses host transcription, recruits RNA polymerase II (RNAP II) to viral replication compartments, and alters the phosphorylation state of the RNAP II large subunit. Host transcription repression and RNAP II modifications require expression of viral immediate-early (IE) genes. Efficient modification of the RNAP II large subunit to the intermediately phosphorylated (IIi) form requires expression of ICP22 and the UL13 kinase. We have further investigated the mechanisms by which HSV-1 effects global changes in RNAP II transcription by analyzing the RNAP II holoenzyme. We find that the RNAP II general transcription factors (GTFs) remain abundant after infection and are recruited into viral replication compartments, suggesting that they continue to be involved in viral gene transcription. However, virus infection modifies the composition of the RNAP II holoenzyme, in particular triggering the loss of the essential GTF, TFIIE. Loss of TFIIE from the RNAP II holoenzyme requires viral IE gene expression, and viral IE proteins may be redundant in mediating this effect. Although viral IE proteins do not associate with the RNAP II holoenzyme, they interact with RNAP II in complexes of lower molecular mass. As the RNAP II holoenzyme containing TFIIE is necessary for activated transcription initiation and RNAP II large subunit phosphorylation in uninfected cells, virus-induced modifications to the holoenzyme may affect both of these processes, leading to aberrant phosphorylation of the RNAP II large subunit and repression of host gene transcription.Herpes simplex virus type 1 (HSV-1) is a 152-kb doublestranded DNA virus, the genome of which is transcribed and replicated within the host cell's nucleus (reviewed in reference 54). During lytic infection, the HSV-1 genes are transcribed by the host's RNA polymerase II (RNAP II) transcription machinery (20, 71). The HSV-1 genes are expressed in a regulated cascade and are classified into three groups based on their order of expression: immediate-early (IE), delayed-early (DE), and late (L). The five IE genes (encoding ICP4, ICP0, ICP27, ICP22, and ICP47) are expressed immediately after infection, and all IE gene products except ICP47 are regulatory proteins involved in controlling expression of the DE and L genes. Their synthesis reaches a peak between 2 and 4 h postinfection, but IE proteins persist throughout infection.Infection with HSV-1 results in dramatic alterations to host gene transcription. Within 6 h postinfection, RNAP II transcription of many, if not most, cellular genes is repressed to less than 40% of uninfected levels (36,61,64,66), and transcription levels decline for at least another 6 h. At the same time, RNAP II transcription of HSV-1 genes is induced to high levels (20, 64). We have shown that repression of host gene transcription does not require DE or L gene transcription or viral DNA replication. Also, virion components do not trigger host transcription repression in the absence of viral IE gen...

All nuclear RNA synthesis is repressed during the mitotic phase of the cell cycle. In addition, RNA polymerase II (RNAP II), nascent RNA and many transcription factors disengage from DNA during mitosis. It has been proposed that mitotic transcription repression and disengagement of factors are due to either mitotic chromatin condensation or biochemical modifications to the transcription machinery. In this study, we investigate the requirement for chromatin condensation in establishing mitotic transcription repression and factor loss, by analyzing transcription and RNAP II localization in mitotic cells infected with herpes simplex virus type 1. We find that virus-infected cells enter mitosis and that mitotic viral DNA is maintained in a nucleosome-free and noncondensed state. Our data show that RNAP II transcription is repressed on cellular genes that are condensed into mitotic chromosomes and on viral genes that remain nucleosome free and noncondensed. Although RNAP II may interact indirectly with viral DNA during mitosis, it remains transcriptionally unengaged. This study demonstrates that mitotic repression of transcription and loss of transcription factors from mitotic DNA can occur independently of nucleosomal chromatin condensation.