The retinoblastoma gene product regulates progression through the G1 phase of the cell cycle.
The RB gene product is a nuclear phosphoprotein that undergoes cell cycle-dependent changes in its phosphorylation status. To test whether RB regulates cell cycle progression, purified RB proteins, either full-length or a truncated form containing the T antigen-binding region, were injected into cells. Injection of either protein early in G1 inhibits progression into S phase. Co-injection of anti-RB antibodies antagonizes this effect. Injection of RB into cells arrested at G1/S or late in G1 has no effect on BrdU incorporation, suggesting that RB does not inhibit DNA synthesis in S phase. These results indicate that RB regulates cell proliferation by restricting cell cycle progression at a specific point in G1 and establish a biological assay for RB activity. Neither co-injection of RB with a T antigen peptide nor injection into cells expressing T antigen prevents cells from progressing into S phase, which supports the hypothesis that T antigen binding has functional consequences for RB.
Goodrich
D W
DW
Center for Molecular Medicine, University of Texas Health Science Center, San Antonio 78284-6250.
Wang
N P
NP
Qian
Y W
YW
Lee
E Y
EY
Lee
W H
WH
D000818:Animals; D000956:Antigens, Viral / Q000502:physiology; D016590:Aphidicolin / Q000494:pharmacology; D016367:Baculoviridae / Q000235:genetics; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects*; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D007313:Insecta; D008845:Microinjections; D008856:Microscopy, Fluorescence; D015739:Nocodazole / Q000494:pharmacology; D012516:Osteosarcoma; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000494:pharmacology*; D013539:Simian virus 40 / Q000235:genetics; D014407:Tumor Cells, Cultured
D000956:Antigens, Viral; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D016590:Aphidicolin; D001973:Bromodeoxyuridine; D015739:Nocodazole; D006918:Hydroxyurea