Isolation and characterization of DNA-binding proteins of Yoshida ascites tumour cells

Abstract

DNA-binding proteins from the cytosol and nuclei of Yoshida ascites sarcoma cells were isolated by affinity chromatography on native and denatured DNA-cellulose columns. The proteins that were retained in the columns were eluted by increasing concentrations of NaCl and analysed by electrophoresis in polyacrylamide gels. Two proteins with approximate molecular weights (MW) of 38000 (38K) and 34000 (34K) D showed high affinity for denatured DNA and eluted in large quantities from denatured DNA-cellulose columns. In contrast, only small amounts of 38000 and 34000 D proteins were found to be associated with native DNA and the native DNA-associated 38K and 34K proteins showed higher rate of phosphorylation than the corresponding denatured DNA-binding proteins. The 38000 and 34000 D DNA-binding proteins were present both in nuclei and cytoplasm. These two proteins together comprised over 70% of the total DNA-binding proteins present in the 0.4 M NaCl eluate of the cytoplasmic extracts. DNA-binding proteins of MW 38000 and 34000 D were also present in a methylcholanthrene-induced fibrosarcoma, although in smaller amounts.