1. Human papillomavirus type 16 E1 E4-induced G2 arrest is associated with cytoplasmic retention of active Cdk1/cyclin B1 complexes.
- Author
-
Davy CE, Jackson DJ, Raj K, Peh WL, Southern SA, Das P, Sorathia R, Laskey P, Middleton K, Nakahara T, Wang Q, Masterson PJ, Lambert PF, Cuthill S, Millar JB, and Doorbar J
- Subjects
- Animals, COS Cells, Cell Line, Tumor, Cell Nucleus chemistry, Cyclin B1, Cytoplasm chemistry, DNA Replication, Humans, Keratins metabolism, Oncogene Proteins, Fusion genetics, Papillomaviridae pathogenicity, Point Mutation, Viral Proteins genetics, Virus Replication, CDC2 Protein Kinase metabolism, Cyclin B metabolism, G2 Phase physiology, Oncogene Proteins, Fusion physiology, Papillomaviridae physiology, Viral Proteins physiology
- 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.
- Published
- 2005
- Full Text
- View/download PDF