Incorporation of glycine into protien and nucleic acid fractions of nuclei of liver and hepatoma.

Abstract

Proteins and nucleic acids of nuclei of liver and hepatoma in the rat were separated into three fractions: Fraction I, soluble in 0.05 m sodium citrate; Fraction II, extracted with 1 m NaCl; and Fraction III, the residual fraction. Histones, acid-insoluble proteins, RNA, and DNA were found in each fraction. Specific activities of the protein and nucleic acid fractions of nuclei of liver and a transplanted hepatoma were determined at intervals after intraperitoneal injection of glycine-1-C14. Arginine-rich histones had higher specific activities than lysine-rich histones at 20 hours in liver and tumor, and the lysine-rich and arginine-rich histones of Histone Fraction III had higher specific activities than the corresponding histones of Fraction II in liver at 20 hours. Histone Fractions II and III of liver nuclei exhibited incorporation rates which were much slower than those of the globulin and residual lipoprotein fractions. By contrast with liver, the histones of tumor nuclei attained specific activities which were only slightly below those of the globulin and lipoprotein fractions at most time intervals. However, this accentuation of the incorporation of glycine into histones of tumor nuclei was much less than the corresponding accentuation of incorporation into RNA and DNA. Preliminary observations were made concerning the conservation of the material of the histones and DNA in liver. A quantitatively minor histone fraction (I) of liver nuclei attained in the early intervals higher specific activities and exhibited more rapid turnover than any other protein fraction of the nucleus, suggestive of a possible precursor-role. Some evidence of heterogeneity of this fraction was observed.