ACETYLATION OF H4K4 IS CELL CYCLE REGULATED & MEDIATED BY HAT3 IN T BRUCEI

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 翻译后组蛋白修饰已在几种真核生物中得到深入研究。有人提出，这些修饰构成了一个“组蛋白密码”，指定转录调控的表观遗传信息。由于组蛋白修饰酶的数量有限，意味着冗余较少，布氏锥虫代表了一个很好的系统，在其中可以研究单个组蛋白修饰和组蛋白修饰酶的功能。在本研究中，我们研究了组蛋白H4（H4K4）赖氨酸4的乙酰化，这是T.布鲁氏菌组蛋白。由于T.通过使用布鲁氏菌组蛋白，我们产生了针对乙酰化和未修饰的H4K4的高度特异性抗体。免疫荧光显微镜和Western印迹与分选的细胞显示了强烈的富集未修饰的H4K4在S期，并建议G1/G0-特异性掩蔽的网站，由于非共价结合因子。最后，我们表明，组蛋白乙酰转移酶3（HAT 3）是负责H4K4乙酰化和蛋白质合成抑制剂放线菌酮的细胞治疗导致几乎瞬时损失的未修饰的H4K4网站。由于HAT3位于细胞核内，我们的研究结果表明，新合成的组蛋白H4与未修饰的K4被迅速输入到细胞核中，在那里它被乙酰化，可能是不可逆的。描述这些结果的手稿已经发表： 布氏锥虫HAT3介导组蛋白H4K4乙酰化的细胞周期调控[11]李文，李文. 分子微生物学2008年2月; 67（4）：762 - 71。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Post-translational histone modifications have been studied intensively in several eukaryotes. It has been proposed that these modifications constitute a 'histone code' that specifies epigenetic information for transcription regulation. With a limited number of histone-modifying enzymes, implying less redundancy, Trypanosoma brucei represents an excellent system in which to investigate the function of individual histone modifications and histone-modifying enzymes. In this study, we characterized the acetylation of lysine 4 of histone H4 (H4K4), the most abundant acetylation site in T. brucei histones. Because of the large sequence divergence of T. brucei histones, we generated highly specific antibodies to acetylated and unmodified H4K4. Immunofluorescence microscopy and Western blots with sorted cells revealed a strong enrichment of unmodified H4K4 in S phase and suggested a G1/G0-specific masking of the site, owing to non-covalently binding factors. Finally, we showed that histone acetyltransferase 3 (HAT3) is responsible for H4K4 acetylation and that treatment of cells with the protein synthesis inhibitor cycloheximide led to an almost instantaneous loss of unmodified H4K4 sites. As HAT3 is located inside the nucleus, our findings suggest that newly synthesized histone H4 with an unmodified K4 is imported rapidly into the nucleus, where it is acetylated, possibly irreversibly. A manuscript describing these results has been published: Acetylation of histone H4K4 is cell cycle regulated and mediated by HAT3 in Trypanosoma brucei. Siegel TN, Kawahara T, Degrasse JA, Janzen CJ, Horn D, Cross GA. Mol Microbiol. 2008 Feb;67(4):762-71.