title: Human cytomegalovirus pp71 stimulates cell cycle progression by inducing the proteasome-dependent degradation of the retinoblastoma family of tumor suppressors.
abstract: The oncoproteins of the DNA tumor viruses, adenovirus E1A, simian virus 40 T antigen, and papillomavirus E7, each interact with the retinoblastoma family of tumor suppressors, leading to cell cycle stimulation, apoptosis induction, and cellular transformation. These proteins utilize a conserved LXCXE motif, which is also found in cellular proteins, to target the retinoblastoma family. Here, we describe a herpesvirus protein that shares a subset of the properties of the DNA tumor virus oncoproteins but maintains important differences as well. The human cytomegalovirus pp71 protein employs an LXCXD motif to attack the retinoblastoma family members and induce DNA synthesis in quiescent cells. pp71 binds to and induces the degradation of the hypophosphorylated forms of the retinoblastoma protein and its family members p107 and p130 in a proteasome-dependent manner. However, pp71 does not induce apoptosis and fails to transform cells. Thus, the similarities and differences in comparison to E1A, T antigen, and E7 make pp71 an interesting new tool with which to further dissect the role of the retinoblastoma/E2F pathway in cellular growth control and carcinogenesis.
authors.affiliation: Molecular Biology Department, Princeton University, Princeton, NJ 08544-1014, USA.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Kalejta
authors.forename: Jill T
authors.initials: JT
authors.lastname: Bechtel
authors.forename: Thomas
authors.initials: T
authors.lastname: Shenk
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D020816:Amino Acid Motifs; D000818:Animals; D017209:Apoptosis; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003587:Cytomegalovirus / Q000502:physiology*; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D011499:Protein Processing, Post-Translational; D011506:Proteins; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology; D014764:Viral Proteins / Q000502:physiology*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011480:Protease Inhibitors; D011506:Proteins; C493844:RBL1 protein, human; C493837:RBL2 protein, human; C493839:Rbl2 protein, rat; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D014157:Transcription Factors; D014764:Viral Proteins; C051298:cytomegalovirus phosphoprotein 71kDa; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex