p21 of Kirsten murine sarcoma virus is thermolabile in a viral mutant temperature sensitive for the maintenance of transformation

Abstract

An intracellular protein, p21, in nonproducer cells transformed by either the Kirsten (Ki-MSV) or Harvey (Ha-MSV) strain of murine sarcoma virus was described recently. The p21 was phosphorylated and was coded for by either Ki-MSV or Ha-MSV. The thermal stability of the newly synthesized [35S]methionine-labeled p21 in [mouse and rat] cells transformed by the wild-type Ki-MSV or by a mutant of Ki-MSV (ts 371) which is temperature sensitive in a viral function required for the maintenance of several properties of the transformed phenotype was compared. The immunoprecipitability of the p21 coded for by the ts 371 Ki-MSV was markedly more thermolabile than the p21 of the wild-type Ki-MSV when the cell extracts were heated in vitro. The p21 is probably required for the maintenance of transformation induced by Ki-MSV.