SV40 large T antigen binds preferentially to an underphosphorylated member of the retinoblastoma susceptibility gene product family.
Extracts of monkey cells (CV-1P) synthesizing SV40 large T antigen (T) were immunoprecipitated with monoclonal antibodies to T or p110-114Rb, the product of the retinoblastoma susceptibility gene (Rb). While a family of p110-114Rb proteins can be detected in anti-Rb immunoprecipitates, only one member of this family, p110Rb, was found in anti-T precipitates of these extracts. Identical results were obtained with extracts of CV-1P cells which had been previously mixed in vitro with highly purified T. The p110-114Rb family is composed of two sets--p110Rb, an un- or under-phosphorylated species, and pp112-114Rb, a group of overtly phosphorylated proteins. Thus, T bound preferentially to the un- or underphosphorylated member of the family. In addition, T failed to alter the relative abundances of these species. These results suggest a model in which the growth suppression function of Rb is down modulated either by phosphorylation or T antigen binding.
Ludlow
J W
JW
Division of Neoplastic Disease Mechanisms, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
DeCaprio
J A
JA
Huang
C M
CM
Lee
W H
WH
Paucha
E
E
Livingston
D M
DM
D000952:Antigens, Polyomavirus Transforming / Q000276:immunology / Q000378:metabolism*; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000276:immunology / Q000378:metabolism*; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D012175:Retinoblastoma / Q000235:genetics*
D000952:Antigens, Polyomavirus Transforming; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D010750:Phosphoproteins