title: Mitotic transcription repression in vivo in the absence of nucleosomal chromatin condensation.
abstract: 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.
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta, Canada T6G 1Z2. charlotte.spencer@cancerboard.ab.ca
authors.forename: C A
authors.initials: CA
authors.lastname: Spencer
authors.forename: M J
authors.initials: MJ
authors.lastname: Kruhlak
authors.forename: H L
authors.initials: HL
authors.lastname: Jenkins
authors.forename: X
authors.initials: X
authors.lastname: Sun
authors.forename: D P
authors.initials: DP
authors.lastname: Bazett-Jones
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D001973:Bromodeoxyuridine; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002451:Cell Compartmentation; D002843:Chromatin / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism; D005456:Fluorescent Dyes; D020868:Gene Silencing; D006367:HeLa Cells; D018259:Herpesvirus 1, Human / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization; D007399:Interphase / Q000235:genetics; D008938:Mitosis / Q000235:genetics*; D009707:Nucleosomes / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*; D014779:Virus Replication / Q000235:genetics
chemical_list: D002843:Chromatin; D004279:DNA, Viral; D005456:Fluorescent Dyes; D009707:Nucleosomes; D014157:Transcription Factors; D016203:CDC2 Protein Kinase; D016282:Aspartic Acid Endopeptidases; D001973:Bromodeoxyuridine