Stimulation of DNA polymerase alpha activity by cdk2-phosphorylated Rb protein.
We propose a new role of retinoblastoma protein as a cell growth activator in its phosphorylated form. The hyper-phosphorylated retinoblastoma protein generated by the action of cdk2/cyclin E strongly stimulated the activity of DNA polymerase alpha, but did not stimulate DNA polymerases delta, epsilon, or primase. But, cdk4/cyclin D-phosphorylated retinoblastoma protein showed little stimulation. Hyper-phosphorylated retinoblastoma protein interacted with the catalytic subunit of DNA polymerase alpha, and stabilised DNA polymerase alpha from heat inactivation at 45 degrees C. These results suggest that in G1 phase, hypo-phosphorylated retinoblastoma protein suppresses the progression of cell cycle as a transcription inhibitor, but that after phosphorylation by cdk2/cyclin E at the G1/S boundary, hyper-phosphorylated retinoblastoma protein acts as a cell-cycle promoter by optimising the DNA polymerase alpha reaction.
Takemura
M
M
Laboratory of Cancer Cell Biology, Nagoya University School of Medicine, Nagoya, 466-8550, Japan.
Yamamoto
T
T
Kitagawa
M
M
Taya
Y
Y
Akiyama
T
T
Asahara
H
H
Linn
S
S
Suzuki
S
S
Tamai
K
K
Yoshida
S
S
D000818:Animals; D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D004256:DNA Polymerase I / Q000235:genetics / Q000378:metabolism*; D004257:DNA Polymerase II / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism; D004789:Enzyme Activation; D004795:Enzyme Stability; D006358:Hot Temperature; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018411:Spodoptera / Q000235:genetics; D014162:Transfection
D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D004256:DNA Polymerase I; D004257:DNA Polymerase II; D004258:DNA Polymerase III