Casein kinase II phosphorylation of the human papillomavirus-18 E7 protein is critical for promoting S-phase entry.
The human papillomavirus type 18 E7 protein subverts the pRb/E2F pathway to promote S-phase reentry by postmitotic, differentiated primary human keratinocytes in support of viral DNA amplification. We prepared a panel of HPV-18 E7 mutations in pRb binding or in casein kinase II (CKII) phosphorylation. Our results showed that the ability of E7 binding to pRb correlated with the activation of DNA polymerase alpha or cyclin E to various extents in differentiated keratinocytes of organotypic cultures but was insufficient to induce the proliferating cell nuclear antigen. Proteins mutated in the CKII recognition sequence or in one or both serine substrates (S32 and S34) bound pRb in vitro, but only those with negative charges at these two residues induced proliferating cell nuclear antigen effectively. Nevertheless, unscheduled cellular DNA synthesis occurred very inefficiently relative to the wild-type E7, if at all. Thus, both pRb binding and CKII phosphorylation of E7 are critical for activating cellular genes essential for S-phase entry.
Chien
W M
WM
Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 35294-0005, USA.
Parker
J N
JN
Schmidt-Grimminger
D C
DC
Broker
T R
TR
Chow
L T
LT
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D047390:Casein Kinase II; D002460:Cell Line; D002478:Cells, Cultured; D019927:Cyclin E / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004256:DNA Polymerase I / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins; D006801:Humans; D007231:Infant, Newborn; D015603:Keratinocytes / Q000378:metabolism* / Q000821:virology; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D009856:Oncogene Proteins, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D050720:Retinoblastoma-Like Protein p107; D016196:S Phase; D016415:Sequence Alignment; D015533:Transcriptional Activation
C493956:CDKN1A protein, human; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; C052633:E7 protein, Human papillomavirus type 18; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D018809:Proliferating Cell Nuclear Antigen; D050720:Retinoblastoma-Like Protein p107; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D004256:DNA Polymerase I