title: The human cytomegalovirus gene products essential for late viral gene expression assemble into prereplication complexes before viral DNA replication.
abstract: The regulation of human cytomegalovirus (HCMV) late gene expression by viral proteins is poorly understood, and these viral proteins could be targets for novel antivirals. HCMV open reading frames (ORFs) UL79, -87, and -95 encode proteins with homology to late gene transcription factors of murine gammaherpesvirus 68 ORFs 18, 24, and 34, respectively. To determine whether these HCMV proteins are also essential for late gene transcription of a betaherpesvirus, we mutated HCMV ORFs UL79, -87, and -95. Cells were infected with the recombinant viruses at high and low multiplicities of infection (MOIs). While viral DNA was detected with the recombinant viruses, infectious virus was not detected unless the wild-type viral proteins were expressed in trans. At a high MOI, mutation of ORF UL79, -87, or -95 had no effect on the level of major immediate-early (MIE) gene expression or viral DNA replication, but late viral gene expression from the UL44, -75, and -99 ORFs was not detected. At a low MOI, preexpression of UL79 or -87, but not UL95, in human fibroblast cells negatively affected the level of MIE viral gene expression and viral DNA replication. The products of ORFs UL79, -87, and -95 were expressed as early viral proteins and recruited to prereplication complexes (pre-RCs), along with UL44, before the initiation of viral DNA replication. All three HCMV ORFs are indispensable for late viral gene expression and viral growth. The roles of UL79, -87, and -95 in pre-RCs for late viral gene expression are discussed.
authors.affiliation: Division of Virology, Aichi Cancer Center Research Institute, 1-1, Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan. hisomura@aichi-cc.jp
authors.forename: Hiroki
authors.initials: H
authors.lastname: Isomura
authors.forename: Mark F
authors.initials: MF
authors.lastname: Stinski
authors.forename: Takayuki
authors.initials: T
authors.lastname: Murata
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Teru
authors.initials: T
authors.lastname: Kanda
authors.forename: Shinya
authors.initials: S
authors.lastname: Toyokuni
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tsurumi
mesh_terms: D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology*; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000821:virology; D015967:Gene Expression Regulation, Viral; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D016366:Open Reading Frames / Q000235:genetics / Q000502:physiology*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; C072217:ICP36 protein, Cytomegalovirus; D017874:Immediate-Early Proteins; D014764:Viral Proteins