title: Herpes simplex virus 1 ICP22 inhibits the transcription of viral gene promoters by binding to and blocking the recruitment of P-TEFb.
abstract: ICP22 is a multifunctional herpes simplex virus 1 (HSV-1) immediate early protein that functions as a general repressor of a subset of cellular and viral promoters in transient expression systems. Although the exact mechanism of repression remains unclear, this protein induces a decrease in RNA polymerase II Serine 2 (RNAPII Ser-2) phosphorylation, which is critical for transcription elongation. To characterize the mechanism of transcriptional repression by ICP22, we established an in vivo transient expression reporter system. We found that ICP22 inhibits transcription of the HSV-1 α, β and γ gene promoters. The viral tegument protein VP16, which plays vital roles in initiation of viral gene expression and viral proliferation, can overcome the inhibitory effect of ICP22 on α-gene transcription. Further immunoprecipitation studies indicated that both ICP22 and VP16 bind to positive transcription elongation factor b (P-TEFb) and form a complex with it in vivo. We extended this to show that P-TEFb regulates transcription of the viral α-gene promoters and affects transcriptional regulation of ICP22 and VP16 on the α-genes. Additionally, ChIP assays demonstrated that ICP22 blocks the recruitment of P-TEFb to the viral promoters, while VP16 reverses this blocking effect by recruiting P-TEFb to the viral α-gene promoters through recognition of the TAATGARAT motif. Taken together, our results suggest that ICP22 interacts with and blocks the recruitment of P-TEFb to viral promoter regions, which inhibits transcription of the viral gene promoters. The transactivator VP16 binds to and induces the recruitment of P-TEFb to viral α-gene promoters, which counteracts the transcriptional repression of ICP22 on α-genes by recruiting p-TEFb to the promoter region.
authors.affiliation: Institute of Medical Biology, Chinese Academy of Medicine Science, Peking Union Medical College, Kunming, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Guo
authors.forename: Wen-juan
authors.initials: WJ
authors.lastname: Wu
authors.forename: Long-ding
authors.initials: LD
authors.lastname: Liu
authors.forename: Li-chun
authors.initials: LC
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Lian-qiu
authors.initials: LQ
authors.lastname: Wu
authors.forename: Ying
authors.initials: Y
authors.lastname: Guan
authors.forename: Qi-han
authors.initials: QH
authors.lastname: Li
mesh_terms: D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002522:Chlorocebus aethiops; D006224:Cricetinae; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D005814:Genes, Viral; D006367:HeLa Cells; D006561:Herpes Simplex / Q000821:virology*; D017405:Herpes Simplex Virus Protein Vmw65 / Q000378:metabolism / Q000502:physiology; D018259:Herpesvirus 1, Human / Q000235:genetics* / Q000502:physiology; D054884:Host-Pathogen Interactions; D006801:Humans; D017874:Immediate-Early Proteins / Q000502:physiology*; D049410:Luciferases, Renilla / Q000096:biosynthesis / Q000235:genetics; D042925:Positive Transcriptional Elongation Factor B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014158:Transcription, Genetic; D014709:Vero Cells
chemical_list: D017405:Herpes Simplex Virus Protein Vmw65; C057294:ICP22 protein, human herpesvirus 1; D017874:Immediate-Early Proteins; D049410:Luciferases, Renilla; D042925:Positive Transcriptional Elongation Factor B