BACKGROUND Establishment of chromosomal cytosine methylation and histone methylation patterns are critical epigenetic modifications required for heterochromatin formation in the mammalian genome. However, the nature of the primary signal(s) targeting DNA methylation at specific genomic regions is not clear. Notably, whether histone methylation and/or chromatin remodeling proteins play a role in the establishment of DNA methylation during gametogenesis is not known. The chromosomes of mouse neonatal spermatogonia display a unique pattern of 5-methyl cytosine staining whereby centromeric heterochromatin is hypo-methylated whereas chromatids are strongly methylated. Thus, in order to gain some insight into the relationship between global DNA and histone methylation in the germ line we have used neonatal spermatogonia as a model to determine whether these unique chromosomal DNA methylation patterns are also reflected by concomitant changes in histone methylation. RESULTS Our results demonstrate that histone H3 tri-methylated at lysine 9 (H3K9me3), a hallmark of constitutive heterochromatin, as well as the chromatin remodeling protein ATRX remained associated with pericentric heterochromatin regions in spite of their extensive hypo-methylation. This suggests that in neonatal spermatogonia, chromosomal 5-methyl cytosine patterns are regulated independently of changes in histone methylation, potentially reflecting a crucial mechanism to maintain pericentric heterochromatin silencing. Furthermore, chromatin immunoprecipitation and fluorescence in situ hybridization, revealed that ATRX as well as H3K9me3 associate with Y chromosome-specific DNA sequences and decorate both arms of the Y chromosome, suggesting a possible role in heterochromatinization and the predominant transcriptional quiescence of this chromosome during spermatogenesis. CONCLUSION These results are consistent with a role for histone modifications and chromatin remodeling proteins such as ATRX in maintaining transcriptional repression at constitutive heterochromatin domains in the absence of 5-methyl cytosine and provide evidence suggesting that the establishment and/or maintenance of repressive histone and chromatin modifications at pericentric heterochromatin following genome-wide epigenetic reprogramming in the germ line may precede the establishment of chromosomal 5-methyl cytosine patterns as a genomic silencing strategy in neonatal spermatogonia.

中文翻译：

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ATRX 与中心异染色质和新生小鼠精原细胞 Y 染色体的关联。

背景染色体胞嘧啶甲基化和组蛋白甲基化模式的建立是哺乳动物基因组中异染色质形成所需的关键表观遗传修饰。然而，在特定基因组区域靶向 DNA 甲基化的主要信号的性质尚不清楚。值得注意的是，组蛋白甲基化和/或染色质重塑蛋白是否在配子发生过程中 DNA 甲基化的建立中发挥作用尚不清楚。小鼠新生儿精原细胞的染色体显示出独特的 5-甲基胞嘧啶染色模式，着丝粒异染色质是低甲基化的，而染色单体是强甲基化的。因此，为了深入了解整体 DNA 与种系中组蛋白甲基化之间的关系，我们使用新生儿精原细胞作为模型来确定这些独特的染色体 DNA 甲基化模式是否也反映在组蛋白甲基化的伴随变化中。结果 我们的结果表明，组蛋白 H3 在赖氨酸 9 (H3K9me3) 处三甲基化，这是组成型异染色质的标志，以及染色质重塑蛋白 ATRX 仍然与中心异染色质区域相关，尽管它们有广泛的低甲基化。这表明在新生儿精原细胞中，染色体 5-甲基胞嘧啶模式的调节独立于组蛋白甲基化的变化，这可能反映了维持中心异染色质沉默的关键机制。此外，