Increased phosphorylation and dimethylation of XY body histones in the Hr6b-knockout mouse is associated with derepression of the X chromosome
Increased phosphorylation and dimethylation of XY body histones in the Hr6b-knockout mouse is associated with derepression of the X chromosome
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DOI：
10.1242/jcs.03451
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发表时间：
2007-06-01
影响因子：
4
通讯作者：
Grootegoed, J. Anton
中科院分区：
文献类型：
--
作者：
Baarends, Willy M.;Wassenaar, Evelyne;Grootegoed, J. Anton
单泛素化的H2A标记在雄性减数分裂前期转录沉默的XY体。与H2A（K119ub1）一起，泛素缀合酶HR6B也富集在XY体上。我们分析了Hr6b基因敲除小鼠精母细胞中H2A和H2B的泛素化，但没有检测到全局变化。接下来，我们分析了苏氨酸残基T120和T119的磷酸化，它们分别与H2A和H2B中泛素化的K119和K120靶位点相邻。在野生型细胞中，H2A（T120ph）和H2B（T119ph）标记减数分裂未配对和沉默的染色质，包括XY体。在Hr6b基因敲除的精母细胞中，H2B（T119ph）信号没有变化，但H2A（T120ph）从粗线期晚期到中期I增强。此外，我们发现增加的H3（K4）二甲基化的双线期Hr6b基因敲除精母细胞的X和Y染色体上，持续到减数分裂后的圆形精子细胞。在这些细胞中，X和Y染色体保持不变的H3（K9 m2）水平，即使这种修饰从着丝粒异染色质中消失。基因表达分析表明，在减数分裂后Hr6b基因敲除精子细胞的X染色体基因的去阻遏。我们的结论是HR6B发挥控制不同的组蛋白修饰精母细胞和精子细胞，这种功能有助于减数分裂后维持X染色体沉默。
Mono-ubiquitylated H2A marks the transcriptionally silenced XY body during male meiotic prophase. Concomitant with H2A(K119ub1), the ubiquitin-conjugating enzyme HR6B is also enriched on the XY body. We analyzed H2A and H2B ubiquitylation in Hr6b-knockout mouse spermatocytes, but no global changes were detected. Next, we analyzed phosphorylation of the threonine residues T120 and T119 that are adjacent to the K119 and K120 target sites for ubiquitylation in H2A and H2B, respectively. In wild-type cells, H2A(T120ph) and H2B(T119ph) mark meiotically unpaired and silenced chromatin, including the XY body. In Hr6b-knockout spermatocytes, the H2B(T119ph) signal was unchanged, but H2A(T120ph) was enhanced from late pachytene until metaphase I. Furthermore, we found increased H3(K4) dimethylation on the X and Y chromosomes of diplotene Hr6b-knockout spermatocytes, persisting into postmeiotic round spermatids. In these cells, the X and Y chromosomes maintained an unchanged H3(K9m2) level, even when this modification was lost from centromeric heterochromatin. Analysis of gene expression showed derepression of X chromosome genes in postmeiotic Hr6b-knockout spermatids. We conclude that HR6B exerts control over different histone modifications in spermatocytes and spermatids, and that this function contributes to the postmeiotic maintenance of X chromosome silencing.