Regulation of bovine papillomavirus replicative helicase e1 by the ubiquitin-proteasome pathway.
Papillomaviruses maintain their genomes in a relatively constant copy number as stable extrachromosomal plasmids in the nuclei of dividing host cells. The viral initiator of replication, E1, is not detected in papillomavirus-infected cells. Here, we present evidence that E1 encoded by bovine papillomavirus type 1 is an unstable protein that is degraded through the ubiquitin-proteasome pathway. In a cell-free system derived from Xenopus egg extracts, E1 degradation is regulated by both cyclin E/Cdk2 binding and E1 replication activity. Free E1 is readily ubiquitinated and degraded by the proteasome, while it becomes resistant to this degradation pathway when bound to cyclin E/Cdk2 complexes before the start of DNA synthesis. This stabilization is reversed in a process involving E1-dependent replication activity. In transiently transfected cells, E1 is also polyubiquitinated and accumulates when proteasome activity is inhibited. Thus, the establishment and maintenance of a stable number of papillomavirus genomes in latently infected cells are in part a function of regulated ubiquitin-mediated degradation of E1.
Malcles
Marie-Helene
MH
Centre de Recherches de Biochimie Macromoléculaire, CNRS, IFR 24, 34 293 Montpellier Cedex 5, France.
Cueille
Nathalie
N
Mechali
Francisca
F
Coux
Olivier
O
Bonne-Andrea
Catherine
C
D000818:Animals; D052688:Bovine papillomavirus 1 / Q000201:enzymology*; D042846:CDC2-CDC28 Kinases; D019556:COS Cells; D002417:Cattle; D002460:Cell Line; D002474:Cell-Free System; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*; D014981:Xenopus / Q000196:embryology; D029867:Xenopus Proteins
D019927:Cyclin E; D004268:DNA-Binding Proteins; C069814:E1 protein, Bovine papillomavirus; D009097:Multienzyme Complexes; D025801:Ubiquitin; D014764:Viral Proteins; D029867:Xenopus Proteins; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495891:Cdk2 protein, Xenopus; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D004265:DNA Helicases