中科院上海生命科學(xué)研究院植生生態(tài)所植物分子遺傳國家重點(diǎn)實(shí)驗(yàn)室方玉達(dá)研究組通過研究,，發(fā)現(xiàn)了組蛋白變體H3.3分子中決定其嵌入核小體和從核小體上解離的信號氨基酸,。
組蛋白變體嵌入核小體形成了結(jié)構(gòu)和功能各異的核小體，在生物體表觀遺傳過程中起非常重要的作用,。組蛋白H3家族包括H3.1,、H3.3和著絲粒特異的CenH3，它們在從果蠅到人類和植物中都非常保守,。H3.3主要通過與一些分子伴侶如HIRA,、DAXX、ATRX以及DEK等作用,，從而代替H3.1與轉(zhuǎn)錄活化的染色質(zhì)結(jié)合,，在生殖細(xì)胞的發(fā)育、表觀遺傳記憶和染色質(zhì)重塑等方面發(fā)揮重要的作用,。擬南芥組蛋白H3.3與H3.1只有四個(gè)氨基酸的不同,，分別是N-端的31和41位以及組蛋白核心區(qū)的87和90位。
通過對擬南芥組蛋白H3.3和H3.1及它們的突變蛋白在核仁rDNA上精細(xì)的細(xì)胞生物學(xué)動態(tài)分析,，方玉達(dá)領(lǐng)導(dǎo)的研究組提出和證實(shí)了這樣一個(gè)模型：即處于組蛋白H3.3核心區(qū)域的87位和90位氨基酸介導(dǎo)了核小體的組裝,，而位于N端的31位和41位氨基酸則介導(dǎo)了核小體的去組裝。
由于組蛋白變體H3.3及其相關(guān)的核小體在不同生物體中的高度保守性,，因此該結(jié)果具有較廣泛的生物學(xué)意義,。
相關(guān)研究論文于6月13日在線發(fā)表于美國《國家科學(xué)院院刊》（PNAS）,。該工作得到了中國科學(xué)院知識創(chuàng)新工程、植物分子遺傳國家重點(diǎn)實(shí)驗(yàn)室,、國家自然科學(xué)基金等的支持,。（生物谷Bioon.com）
生物谷推薦原文出處：
Proceedings of the National Academy of Sciences DOI： 10.1073/pnas.1017882108
Four amino acids guide the assembly or disassembly of Arabidopsis histone H3.3-containing nucleosomes
Shi, Leilei; Wang, Jing; Hong, Fang; Spector, David L.; Fang, Yuda
The histone variant H3.3 and the canonical histone H3.1, which differ in only 4- to 5-aa positions, are coexpressed in complexmulticellular eukaryotes from fly to human and plant. H3.3 is mainly associated with active chromatin by replacing H3.1 throughchaperones such as histone regulator A, death domain associated protein DAXX, thalassemia/mental retardation syndrome X-linkedhomolog ATRX, or proto-oncogene protein DEK and plays important roles in the germline, epigenetic memory, and reprogramming.However, the signals within H3.3 that serve as a guide for its dynamic deposition or depletion in plant chromatin are notclear. Here, we show that Arabidopsis histone H3.3 differs from H3.1 by 4-aa sites: amino acids 31, 41, 87, and 90. Although histone H3.1 is highly enriched inchromocenters, H3.3 is present in nucleolar foci in addition to being diffusely distributed in the nucleoplasm. We have evaluatedthe function of the 4 aa that differ between H3.1 and H3.3. We show that amino acid residue 87, and to some extent residue90, of Arabidopsis histone H3.3 are critical for its deposition into rDNA arrays. When RNA polymerase I-directed nucleolar transcription isinhibited, wild type H3.3, but not H3.3 containing mutations at residues 31 and 41, is depleted from the rDNA arrays. Together,our results are consistent with a model in which amino acids 87 and 90 in the core domain of H3.3 guide nucleosome assembly,whereas amino acids 31 and 41 in the N-terminal tail of Arabidopsis H3.3 guide nucleosome disassembly in nucleolar rDNA.
