title: Human papillomavirus type 16 E1 E4-induced G2 arrest is associated with cytoplasmic retention of active Cdk1/cyclin B1 complexes.
abstract: Human papillomavirus type 16 (HPV16) can cause cervical cancer. Expression of the viral E1 E4 protein is lost during malignant progression, but in premalignant lesions, E1 E4 is abundant in cells supporting viral DNA amplification. Expression of 16E1 E4 in cell culture causes G2 cell cycle arrest. Here we show that unlike many other G2 arrest mechanisms, 16E1 E4 does not inhibit the kinase activity of the Cdk1/cyclin B1 complex. Instead, 16E1 E4 uses a novel mechanism in which it sequesters Cdk1/cyclin B1 onto the cytokeratin network. This prevents the accumulation of active Cdk1/cyclin B1 complexes in the nucleus and hence prevents mitosis. A mutant 16E1 E4 (T22A, T23A) which does not bind cyclin B1 or alter its intracellular location fails to induce G2 arrest. The significance of these results is highlighted by the observation that in lesions induced by HPV16, there is evidence for Cdk1/cyclin B1 activity on the keratins of 16E1 E4-expressing cells. We hypothesize that E1 E4-induced G2 arrest may play a role in creating an environment optimal for viral DNA replication and that loss of E1 E4 expression may contribute to malignant progression.
authors.affiliation: Division of Virology, National Institute for Medical Research, London, NW7 1AA, United Kingdom.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Davy
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Jackson
authors.forename: Kenneth
authors.initials: K
authors.lastname: Raj
authors.forename: Woei Ling
authors.initials: WL
authors.lastname: Peh
authors.forename: Shirley A
authors.initials: SA
authors.lastname: Southern
authors.forename: Papia
authors.initials: P
authors.lastname: Das
authors.forename: Rina
authors.initials: R
authors.lastname: Sorathia
authors.forename: Peter
authors.initials: P
authors.lastname: Laskey
authors.forename: Kate
authors.initials: K
authors.lastname: Middleton
authors.forename: Tomomi
authors.initials: T
authors.lastname: Nakahara
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Masterson
authors.forename: Paul F
authors.initials: PF
authors.lastname: Lambert
authors.forename: Scott
authors.initials: S
authors.lastname: Cuthill
authors.forename: Jonathan B A
authors.initials: JB
authors.lastname: Millar
authors.forename: John
authors.initials: J
authors.lastname: Doorbar
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D019556:COS Cells; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000737:chemistry; D019926:Cyclin B / Q000378:metabolism*; D056744:Cyclin B1; D003593:Cytoplasm / Q000737:chemistry; D004261:DNA Replication; D016195:G2 Phase / Q000502:physiology*; D006801:Humans; D007633:Keratins / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000502:physiology*; D027383:Papillomaviridae / Q000472:pathogenicity / Q000502:physiology*; D017354:Point Mutation; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology*; D014779:Virus Replication
chemical_list: C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D015514:Oncogene Proteins, Fusion; D014764:Viral Proteins; C072777:oncogene protein E1--E4, Human papillomavirus type 16; D007633:Keratins; D016203:CDC2 Protein Kinase