SDS-polyacrylamide gel electrophoresis of the nuclear matrix proteins showed a predominance of high molecular weight and low molecular weight polypeptides in the nuclear matrices of hepatomas and cultured Chinese hamster fibroblasts as compared to quiescent and regenerating rat liver. These features were more prominent in solid hepatoma 27 than in Zajdela ascites hepatoma or in cultured cells. In proliferating cells (tumors, regenerating liver, log phase cell culture) a polypeptide band of 150 kD and lamin B were conspicuous at the expense of lamins A and C.
Our previous studies showed a predominance of high molecular weight protein group in tumor nuclear matrices. Contrary to normal cells, proteins of this group are preferentially phosphorylated. Phosphoproteins of hepatoma nuclear matrix are selectively subjected to rapid proteolysis. By alkali treatment and a monoclonal antibody against phosphotyrosyl residue the presence of two high molecular weight bands of phosphotyrosyl-containing proteins was detected in nuclear matrices of tumor but not of normal liver cells. High molecular weight protein group of tumor nuclear matrices revealed also a rapid turnover and preferential incorporation of labeled amino acids selectively inhibited by chloramphenicol.
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