Human papillomavirus E7 oncoproteins bind a single form of cyclin E in a complex with cdk2 and p107.
The E6 and E7 proteins of the high-risk human papillomaviruses (HPVs) act coordinately to immortalize human keratinocytes. These viral oncoproteins function by binding and altering the activity of cellular proteins which regulate cell cycle progression. Among the proteins bound by E7 are the retinoblastoma protein, Rb, as well as the related p107 and p130 proteins. In addition, E7 binds cyclin A, which regulates transit through the S and G2/M phases of the cell cycle. In this study, we demonstrate that HPV 18 E7 also associates with cyclin E which controls the G1/S transition. E7/cyclin E complexes were immunoprecipitated from E7-expressing cells as well as from cell extracts using GST-E7 fusion proteins. E7 was found to complex with a single form of cyclin E, and the binding was mediated through p107. Both E7/cyclin E and E7/cyclin A complexes exhibit kinase activity through associated cdk2 proteins which can contribute to phosphorylation of p107. The association of E7 with proteins which regulate transit through the cell cycle may provide an additional mechanism by which infection with human papillomaviruses results in cellular hyperproliferation.
McIntyre
M C
MC
Department of Microbiology-Immunology, Northwestern University, Chicago, Illinois 60611, USA.
Ruesch
M N
MN
Laimins
L A
LA
D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000502:physiology; D002460:Cell Line; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism*; D004268:DNA-Binding Proteins; D016193:G1 Phase / Q000502:physiology; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism*; D050720:Retinoblastoma-Like Protein p107; D016196:S Phase / Q000502:physiology
D016213:Cyclins; D004268:DNA-Binding Proteins; C052633:E7 protein, Human papillomavirus type 18; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; C493844:RBL1 protein, human; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D005982:Glutathione Transferase; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases