Hendzel M J, Davie J R
Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
J Biol Chem. 1989 Nov 15;264(32):19208-14.
The relationship between histone methylation and the transcriptionally active chromatin state was investigated. Immature chicken erythrocytes, which were obtained from the peripheral blood of anemic birds, were incubated with L-[methyl-3H]methionine and cycloheximide. Under these conditions histones H3 and H4 are methylated. The erythrocyte nuclei were incubated with micrococcal nuclease, and the chromatin fragments were fractionated according to their solubility in EDTA and 0.15 M NaCl. Chromatin fractions, which were enriched in transcriptionally active genes, were enriched in methylated histones. Moreover, the acetylated species of histones H3 and H4, which are complexed with active genes (Hebbes, T. R., Thorne, A. W., and Crane-Robinson, C. (1988) EMBO J. 7, 1395-1402), were preferentially methylated. The methylation of these histones was not dependent on ongoing transcription. The distribution of histone H3 methyltransferase activity among the various chromatin regions was also studied. This enzyme activity was greatest for the chromatin fragments that were enriched in active/competent genes. However, our results suggest that histone H3 methyltransferase is bound to the nucleosome. The enzyme, which may be localized in the active gene chromatin domains, may ensure that the histones associated with active genes are methylated. Histone methylation, which has a slow turnover rate, may contribute to the maintenance of the transcriptionally active chromatin state.
研究了组蛋白甲基化与转录活性染色质状态之间的关系。从贫血鸟类外周血中获取的未成熟鸡红细胞，用L-[甲基-³H]甲硫氨酸和环己酰亚胺进行孵育。在这些条件下，组蛋白H3和H4会发生甲基化。将红细胞核与微球菌核酸酶一起孵育，然后根据染色质片段在EDTA和0.15 M NaCl中的溶解性进行分级分离。富含转录活性基因的染色质级分中富含甲基化组蛋白。此外，与活性基因结合的组蛋白H3和H4的乙酰化形式（Hebbes, T. R., Thorne, A. W., and Crane-Robinson, C. (1988) EMBO J. 7, 1395 - 1402）优先发生甲基化。这些组蛋白的甲基化不依赖于正在进行的转录。还研究了组蛋白H3甲基转移酶活性在不同染色质区域的分布。这种酶活性在富含活性/潜在活性基因的染色质片段中最高。然而，我们的结果表明组蛋白H3甲基转移酶与核小体结合。该酶可能定位于活性基因染色质结构域，可确保与活性基因相关的组蛋白发生甲基化。组蛋白甲基化的周转速度较慢，可能有助于维持转录活性染色质状态。
