Nuclear proteins: I. Electrophoretic comparison of mouse nucleoli, heterochromatin, euchromatin and contractile proteins

Abstract

Summary A number of observations suggest there are some non-histone protein unique to constitutive heterochromatin which are responsible for some of its properties such as interphase condensation, C-banding, frequent decreased quinacrine fluorescence, ectopic pairing, and ability to cause position effect. To investigate this, mouse nuclei were disrupted by sonication and separated by differential centrifugation into heterochromatin+nucleoli, heterochromatin, intermediate, euchromatin pellet and euchromatin supernatant fractions. The non-histone proteins of these fractions were examined by SDS slab gel electrophoresis and compared with the proteins of the cytoplasm, nucleoplasm, cytoplasmic ribosomes, nuclear membrane, and to tubulin, actin, myosin and other muscle proteins. There were a number of non-histone proteins that were unique to or present in greater quantity in the hterochromatin+nucleoli fraction than in the euchromatin. Some of the chromatin non-histone proteins co-migrated with muscle proteins by SDS gel electrophoresis.