Human papillomavirus type 16 E1 E4-induced G2 arrest is associated with cytoplasmic retention of active Cdk1/cyclin B1 complexes.
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.
Davy
Clare E
CE
Division of Virology, National Institute for Medical Research, London, NW7 1AA, United Kingdom.
Jackson
Deborah J
DJ
Raj
Kenneth
K
Peh
Woei Ling
WL
Southern
Shirley A
SA
Das
Papia
P
Sorathia
Rina
R
Laskey
Peter
P
Middleton
Kate
K
Nakahara
Tomomi
T
Wang
Qian
Q
Masterson
Phillip J
PJ
Lambert
Paul F
PF
Cuthill
Scott
S
Millar
Jonathan B A
JB
Doorbar
John
J
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
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