Histone Modifications and Their Relationship to Constitutive Heterochromatin Content in Cultured Peromyscus Cells

摘要

Biochemical research in recent years has provided evidence that control of genetic activity in eucaryotic cells may be accomplished by the modulation of chromatin structure caused by reversible modifications of chromatin proteins, in particular, the histones. In order to test the hypothesis that biochemical modifications of histone proteins are involved in condensation of chromatin (heterochromatization) histones were analyzed from three cultured cell lines from mice of the genus Peromyscus. Radiolabeled histones extracted from these cell lines were analyzed using preparative polyacrylamide gel electrophoresis with non-ionic detergent present to facilitate separation of hydrophobic histone variants. It was found that P. eremicus cells, which contain 34% more heterochromatin that P. boylii cells, also contain a larger proportion of the more hydrophobic H2A variant (MHP-H2A). This MHP-H2A variant was also two times more phosphorylated than the other, less hydrophobic H2A variant (LHP-H2A) in these cell lines. When unlabeled histones were extracted and subjected to analytical polyacrylamide gel electrophoresis, it was found that these high heterochromatin P. eremicus cells also contained 28 to 35% more unacetylated H4, 22 to 29% more unacetylated H3, and 18 to 22% more unacetylated H2B than low heterochromatin cells (P. bovlii, P. crinitus). Thus, histone acetylation was found to be inversely proportional to constitutive heterochromatin content in these cell lines. Certain histone modifications were thus found to be related to constitutive heterochromatization in these cell lines. (ERA citation 05:029678)