PUTATIVE NUCLEAR CDK2 SUBSTRATES IN NORMAL AND TRANSFORMED-CELLS

The presence of putative substrates of cdk2 in a nuclear fraction obta ined by DNase plus RNase extraction (S1 fraction) has been analyzed by immunoprecipitation using specific anti-cdk2 antibodies, followed by phosphorylation assays. S1 nuclear fractions from four different cellu lar types, two normal (rat hepatocytes and human T lymphocytes) and tw o transformed (HeLa and Namalwa cells), have been studied. Results ind icate that the normal cells share three putative nuclear cdk2 substrat es of 21, 37 and 57 kDa. On the other hand, only a substrate of 20 kDa is shared by the two transformed cell lines. On comparing the prolife rating normal lymphocytes with the lymphoblastoid cell line Namalwa, i t can be observed that they share two proteins of 40 and 70 kDa. (C) 1 996 Academic Press, Inc.