title: Murine gammaherpesvirus 68 open reading frame 45 plays an essential role during the immediate-early phase of viral replication.
abstract: Murine gammaherpesvirus 68 (MHV-68) has been developed as a model for the human gammaherpesviruses Epstein-Barr virus and human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus (HHV-8/KSHV), which are associated with several types of human diseases. Open reading frame 45 (ORF45) is conserved among the members of the Gammaherpesvirinae subfamily and has been suggested to be a virion tegument protein. The repression of ORF45 expression by small interfering RNAs inhibits MHV-68 viral replication. However, the gene product of MHV-68 ORF45 and its function have not yet been well characterized. In this report, we show that MHV-68 ORF45 is a phosphorylated nuclear protein. We constructed an ORF45-null MHV-68 mutant virus (45STOP) by the insertion of translation termination codons into the portion of the gene encoding the N terminus of ORF45. We demonstrated that the ORF45 protein is essential for viral gene expression immediately after the viral genome enters the nucleus. These defects in viral replication were rescued by providing ORF45 in trans or in an ORF45-null revertant (45STOP.R) virus. Using a transcomplementation assay, we showed that the function of ORF45 in viral replication is conserved with that of its KSHV homologue. Finally, we found that the C-terminal 23 amino acids that are highly conserved among the Gammaherpesvirinae subfamily are critical for the function of ORF45 in viral replication.
authors.affiliation: Department of Molecular and Medical Pharmacology, University of California at Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Qingmei
authors.initials: Q
authors.lastname: Jia
authors.forename: Vasili
authors.initials: V
authors.lastname: Chernishof
authors.forename: Eric
authors.initials: E
authors.lastname: Bortz
authors.forename: Ian
authors.initials: I
authors.lastname: Mchardy
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Wu
authors.forename: Hsiang-I
authors.initials: HI
authors.lastname: Liao
authors.forename: Ren
authors.initials: R
authors.lastname: Sun
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003062:Codon / Q000235:genetics; D016384:Consensus Sequence; D006224:Cricetinae; D018142:Gammaherpesvirinae / Q000235:genetics / Q000502:physiology*; D016679:Genome, Viral; D017874:Immediate-Early Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010443:Peptide Chain Termination, Translational; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000235:genetics; D014779:Virus Replication
chemical_list: D003062:Codon; D017874:Immediate-Early Proteins; C456286:ORF45 protein, Kaposi's sarcoma-associated herpesvirus; C500426:ORF45 protein, murine gammaherpesvirus 68; D014764:Viral Proteins