Formation of facultative heterochromatin in fission yeast

我们研究了裂变酵母兼性异染色质形成的分子机制。我们首先证明了分裂酵母减数分裂基因，mei4和ssm4位点是异染色化的，这是在营养生长中赖氨酸9 （H3K9me）甲基化组蛋白H3的存在所证明的。这种异染色质标记在细胞进入减数分裂细胞周期后消失。我们随后发现，当细胞进入营养生长期时，H3K9me的建立需要mei4和ssm4 mRNA转录物的Mmi1降解机制。此外，我们发现DSRs，一组包含在mei4和ssm4转录本中的mRNA区域，是Mmi1依赖性异染色质建立所必需的。这些结果揭示了我们对真核生物中异染色质形成的理解。

We have studied the molecular mechanism of facultative heterochromatin formation in fission yeast. We first demonstrated that the fission yeast meiotic genes, mei4 and ssm4 loci are heterochromatinated, as evidenced by the presence of histone H3 methylated at lysine 9 (H3K9me), in vegetative growth. This heterochromatin marker disappears upon the entry of cells into meiotic cell cycle. We then revealed that the Mmi1 -degradation machinery of mei4 and ssm4 mRNA transcript is required for the establishment of H3K9me when cells enters vegetative growth phase. Moreover, we found that DSRs, a set of mRNA regions included in mei4 and ssm4 transcripts, are required for the Mmi1 -dependent heterochromatin establishment. These results shed an insight into our understanding of how heterochromatin is formed in eukaryotes.