title: How adeno-associated virus Rep78 protein arrests cells completely in S phase.
abstract: Adeno-associated virus Rep78 protein has antiproliferative effects on cells. It inhibits cell cycle progression, and, in particular, Rep78 induces a complete arrest within S phase, a response rarely seen after cell DNA damage. We examined how Rep78 achieves such an efficient S phase block. Rep78 inhibits Cdc25A activity by a novel means in which binding between the two proteins stabilizes Cdc25A, thus increasing its abundance, while at the same time preventing access to its substrates cyclin-dependent kinase (Cdk) 2 and Cdk1. This effect alone does not induce a complete S phase block. In addition, Rep78, as well as Rep68, produces nicks in the cellular chromatin, inducing a DNA damage response mediated by ataxia telangiectasia mutated (ATM) leading to G(1) and G(2) blocks. Mutational analysis shows that the zinc finger domain and nuclease activity of Rep78 are both required for the S phase block. The results suggest that a true S phase block cannot be achieved through a single pathway, and that adeno-associated virus Rep78 protein arrests cells within S phase by interfering with two pathways that would normally lead to an S phase slow-down.
authors.affiliation: Swiss Institute for Experimental Cancer Research, 1066 Epalinges, Switzerland.
authors.forename: Carole
authors.initials: C
authors.lastname: Berthet
authors.forename: Kenneth
authors.initials: K
authors.lastname: Raj
authors.forename: Philippe
authors.initials: P
authors.lastname: Saudan
authors.forename: Peter
authors.initials: P
authors.lastname: Beard
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D016203:CDC2 Protein Kinase / Q000378:metabolism; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D049109:Cell Proliferation; D002843:Chromatin / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016196:S Phase / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D014764:Viral Proteins; C068734:rep proteins, Adeno-associated virus 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases