PURIFICATION AND PARTIAL CHARACTERIZATION OF NUCLEOLAR ANTIGEN-1 OF NOVIKOFF HEPATOMA

Abstract

A nucleolar chromatin antigen (NoAg-1) found in [rat] Novikoff hepatoma but not in normal liver was purified to homogeneity as shown by 2-dimensional gel electrophoresis. Initial purification of NoAg-1 was partially achieved by isolation of nucleolar chromatin and fractionation of its proteins by successive extraction with solutions of increasing salt concentration. Further purification of this antigen was achieved by affinity and hydroxylapatite chromatography. Although approximately 50% of the NoAg-1 antigen was in the 0.6 M NaCl extract of Novikoff nucleoli, it was less pure than in the 2 M NaCl:5 M urea extract which contained 25% of the NoAg-1 at a purity of 40%. The highly purified NoAg-1 had an approximate MW of 60,000 and pl [isoelectric point] of 5.1; the yield of NoAg-1 was 0.22% of the total nucleolar proteins.