Modulation by Exogenous Histones of Phosphorylation of Non-Histone Nuclear Proteins in Isolated Rat Liver Nuclei

Edward M Johnson,Giorgio Vidali,Virginia C Littau,Vincent G Allfrey

doi:10.1016/s0021-9258(19)43332-2

Abstract

Abstract The phosphorylation of specific non-histone proteins in isolated rat liver nuclei is modified by the addition of exogenous histone fractions. The added histones are quantitatively adsorbed and their presence in the chromatin has been verified by electron microscope autoradiography. Histone fractions F1 and F2A1 stimulate phosphorylation of different nuclear phosphoproteins. F1 stimulates the phosphorylation of a protein fraction with a molecular weight of about 40,000, while F2A1 enhances phosphorylation of a protein fraction with a molecular weight of about 22,000. F1 and F2A1 each inhibit the phosphorylation of a specific low molecular weight nuclear protein fraction. Histones F2A2, F2B and F3 have little effect on the phosphorylation of non-histone proteins under these conditions. The results suggest that individual histones may be involved in the control of phosphorylation of specific non-histone nuclear proteins, particularly at times when the concentrations of nuclear proteins are changing relative to one another.

Highlights

Introduction of IIisiones into Isolated NucleiRat liver nuclei were isolated and exposed to increasing concentrations of individual histone fractions which had been labeled enzymatically with [melhyl-3H]acetate [15]
The results indicate that individual histones differ in their effects on the phosphorylation of specific phosphoproteins of hepatic cell nuclei
For studies of histone intranuclear localization by electron microscope autoradiography, some of the tyrosyl residues of calf thymus histones were iodinated by treatment with lz51 in the presence of an oxidizing agent as follows: 100 mg of total histone were dissolved in 2.0 ml of 0.05 M potassium phosphate buffer at pH 7.4

Summary

Introduction

Introduction of IIisiones into Isolated NucleiRat liver nuclei were isolated and exposed to increasing concentrations of individual histone fractions which had been labeled enzymatically with [melhyl-3H]acetate [15]. The present study is an examination of the effects of exogenous histone fractions upon the phosphorylation of non-histone proteins in isolated rat liver nuclei. -The phosphorylation of nuclear acidic proteins has been followed by incubating isolated rat liver nuclei in the presence of

Results

Conclusion