Synthetic Heterochromatin Bypasses RNAi and Centromeric Repeats to Establish Functional Centromeres
Synthetic Heterochromatin Bypasses RNAi and Centromeric Repeats to Establish Functional Centromeres
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DOI：
10.1126/science.1172026
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发表时间：
2009-06-26
期刊：
影响因子：
56.9
通讯作者：
Allshire, Robin C.
中科院分区：
文献类型：
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作者：
Kagansky, Alexander;Folco, Hernan Diego;Allshire, Robin C.
在裂殖酵母着丝粒的中央结构域中，动粒组装在CENP-A（Cnp 1）核小体上。通常，由侧翼外重复转录物产生的小干扰RNA将组蛋白H3赖氨酸9甲基转移酶Clr 4引导至同源基因座以形成异染色质。建立CENP-AC（np 1）染色质需要外部重复序列、RNA干扰（RNAi）和着丝粒异染色质。我们证明了通过常染色质位点的DNA结合位点束缚Clr 4诱导异染色质组装，有或没有活性RNAi。这种合成的异染色质完全取代了基于质粒的微型染色体上的外部重复序列，促进从头CENP-A（Cnp 1）和动粒组装，以允许它们的有丝分裂分离，即使RNAi无效。因此，外部重复序列在着丝粒建立中的作用仅仅是提供RNAi底物以指导异染色质形成; H3 K9甲基化依赖的异染色质单独足以形成功能性着丝粒。
In the central domain of fission yeast centromeres, the kinetochore is assembled on CENP-A(Cnp1) nucleosomes. Normally, small interfering RNAs generated from flanking outer repeat transcripts direct histone H3 lysine 9 methyltransferase Clr4 to homologous loci to form heterochromatin. Outer repeats, RNA interference (RNAi), and centromeric heterochromatin are required to establish CENP-AC(np1) chromatin. We demonstrated that tethering Clr4 via DNA-binding sites at euchromatic loci induces heterochromatin assembly, with or without active RNAi. This synthetic heterochromatin completely substitutes for outer repeats on plasmid-based minichromosomes, promoting de novo CENP-A(Cnp1) and kinetochore assembly, to allow their mitotic segregation, even with RNAi inactive. Thus, the role of outer repeats in centromere establishment is simply the provision of RNAi substrates to direct heterochromatin formation; H3K9 methylation-dependent heterochromatin is alone sufficient to form functional centromeres.