Extractability of Histones from Formalin-Treated Nuclei of L-Cells

Abstract

Treatment of isolated L-cell nuclei with cold buffered formalin for 40 min was found to decrease the extractability of histones with trypsin and with 0.25 N HCl. Among the various fractions separated on P-60 exclusion chromatography or by acrylamide gel electrophoresis, F1 was found to be preferentially extracted with HCl after formalin treatment, while F2a1 was found to be relatively more resistant to HCl or trypsin extraction in both formalin-treated and control nuclei. In the latter case, however, formalin treatment resulted in a drastic reduction in the effectiveness of trypsin digestion. After treatment for 30 min with trypsin (0.1 mg/ml) in Tris buffer, pH 7.0, only 29% of F2a1 was removed as compared with 85–95% of the other histone fractions. These results are discussed in the context of a possibly more protected localization of histone F2a1 in the chromatin.