RESUMEN
We compared the two-dimensional patterns of nuclear proteins obtained from normal quiescent T lymphocytes with those from normal proliferating T lymphocytes and three lymphoblastoid cell lines (CEM, Namalwa, and Molt-4). We identified sets of nuclear proteins which are specific for normal quiescent or normal proliferating T lymphocytes, or shared by the three lymphoblastoid cell lines and absent from the normal T cells. The protein patterns from two nuclear subfractions, i.e., S1 fraction, obtained after nuclease extraction, and the nuclear matrix, were also analyzed. In S1 nuclear fraction, 6 proteins of 75 kDa [isoelectric point (pI) 4.4], 55 kDa (pI 6.7), 41 kDa (pI 4.1), 39 kDa (pI 5.0), 32 kDa (pI 5.5), and 29 kDa (pI 6.6) were found to be specifically present in normal quiescent cells but not in normal proliferating or lymphoblastoid cell lines. Five proteins of 23 kDa (pI 4.2), 23 kDa (pI 4.3), 22 kDa (pI 4.4), 21 kDa (pI 4.5), and 21 kDa (pI 4.6) were observed only in the S1 fraction of normal proliferating lymphocytes, whereas they were absent in normal quiescent cells and in the transformed cell lines. Eight proteins of 56 kDa (pI 4.7), 50 kDa (pI 4.6), 45 kDa (pI 4.4), 43 kDa (pI 4.3), 42 kDa (pI 4.3), 41 kDa (pI 4.3), 43 kDa (pI 4.2), and 42 kDa (pI 4.1) were found only in the nuclear matrix of normal quiescent cells. Moreover, two doublets of proteins of 31-33 kDa (pI 4.3) and 31-33 kDa (pI 4.2) were found only in the nuclear matrix of the normal proliferating cells and three proteins of 37 kDa (pI 3.8), 37 kDa (pI 3.7), and 35 kDa (pI 4.5) were specifically present in the nuclear matrix of the lymphoblastoid cells lines, but not in normal quiescent or activated lymphocytes.
Asunto(s)
Linfocitos/química , Proteínas Nucleares/análisis , Antígenos Nucleares , División Celular , Línea Celular , Humanos , Linfocitos/citología , Linfocitos T/química , Linfocitos T/citologíaRESUMEN
We report here experimental evidence indicating that the p21CIP, the universal inhibitor of cyclin-dependent protein kinases, general inhibitor CDKs is a substrate oof cyclin A-cdk2. The evidence comes from phosphorylation experiments in which the endogenous p21CIP present in using the original cyclin A-cdk2 complexes immunoprecipitated from HeLa cells extracts can be phosphorylated by the cdk2 of the same complexes. In vitro experiments showing that reconstituted GSTcyclin A-GSTcdk2 complexes from phosphorylate recombinant GSTp21CIP confirms that p21CIP is a cyclin A-cdk2 substrate.