title: General blockade of human cytomegalovirus immediate-early mRNA expression in the S/G2 phase by a nuclear, Daxx- and PML-independent mechanism.
abstract: The onset of human cytomegalovirus (HCMV) lytic replication is strictly controlled by the host cell division cycle. Although viral entry of S/G2-phase cells is unperturbed expression of major immediate-early (MIE) genes IE1 and IE2 is tightly blocked in these cells. Besides the finding that cyclin-dependent kinase (CDK) activity is required for IE1/IE2 repression little is known about the nature of this cell cycle-dependent block. Here, we show that the block occurs after nuclear entry of viral DNA and prevents the accumulation of IE1/IE2 mRNAs, suggesting an inhibition of transcription. Remarkably, the presence of cis-regulatory regions of the MIE locus is neither sufficient nor necessary for IE1/IE2 repression in the S/G2 phase. Furthermore, the block of viral mRNA expression also affects other immediate-early transcribed regions, i.e. the US3 and UL36-38 gene loci. This suggests a mechanism of repression that acts in a general and not a gene-specific fashion. Such a nuclear, genome-wide repression of HCMV is typically mediated by the intrinsic immune defence at nuclear domain 10 (ND10) structures. However, we found that neither Daxx nor PML, the main players of ND10-based immunity, are required for the block to viral gene expression in the S/G2 phase. In addition, the viral tegument protein pp71 (pUL82), a major antagonist of the intrinsic immunity at pre-immediate-early times of infection, proved to be functional in S-phase cells. This suggests the existence of a yet undiscovered, CDK-dependent mechanism exerting higher-level control over immediate-early mRNA expression in HCMV-infected cells.
authors.affiliation: Labor für Pädiatrische Molekularbiologie, Charité-Universitätsmedizin Berlin, Ziegelstr. 5-9, 10117 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Zydek
authors.affiliation: Labor für Pädiatrische Molekularbiologie, Charité-Universitätsmedizin Berlin, Ziegelstr. 5-9, 10117 Berlin, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Uecker
authors.affiliation: Institut für Klinische und Molekulare Virologie der Universität Erlangen-Nürnberg, Schlossgarten 4, 91054 Erlangen, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Tavalai
authors.affiliation: Institut für Klinische und Molekulare Virologie der Universität Erlangen-Nürnberg, Schlossgarten 4, 91054 Erlangen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Stamminger
authors.affiliation: Labor für Pädiatrische Molekularbiologie, Charité-Universitätsmedizin Berlin, Ziegelstr. 5-9, 10117 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Hagemeier
authors.affiliation: Labor für Pädiatrische Molekularbiologie, Charité-Universitätsmedizin Berlin, Ziegelstr. 5-9, 10117 Berlin, Germany.
authors.forename: Lüder
authors.initials: L
authors.lastname: Wiebusch
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D056970:Co-Repressor Proteins; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D003587:Cytomegalovirus / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D016195:G2 Phase; D015967:Gene Expression Regulation, Viral; D017781:Genes, Immediate-Early; D056426:Genetic Loci; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D000071156:Promyelocytic Leukemia Protein; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016196:S Phase; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins / Q000378:metabolism; D014779:Virus Replication
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C094297:CALCOCO2 protein, human; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D004279:DNA, Viral; D017874:Immediate-Early Proteins; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D012333:RNA, Messenger; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D014764:Viral Proteins; C051298:cytomegalovirus phosphoprotein 71kDa; C070576:PML protein, human; D018844:Cyclin-Dependent Kinases