Concentrations of high-mobility-group proteins in the nucleus and cytoplasm of several rat tissues.

Abstract

Nuclear and cytoplasmic fractions were isolated from various tissues of the rat by a nonaqueous technique. The high-mobility-group (HMG) proteins were extracted from these fractions with acid and separated by 1- and 2-dimensional PAGE [polyacrylamide gel electrophoresis]. The concentration of high-mobility-group proteins HMG1, HMG2 and HMG17 in the nucleus and cytoplasm were then estimated from the staining intensities of the electrophoretic bands. The cytoplasmic concentrations of these proteins were very low, usually less than 1/30 of those present in the corresponding nuclear fractions. For the tissues studied (liver, kidney, heart and lung), the concentrations of HMG proteins in the nucleus did not differ significantly from 1 tissue to another. Averaged over the 4 tissues investigated, there were 0.28 molecule of HMG1, 0.18 molecule of HMG2, and 0.46 molecule of HMG17 per nucleosome. These values are considerably higher than those reported previously.