Elucidation of transcriptional repression mechanism for human endogenous retrovirus

众所周知，DNA甲基化和组蛋白甲基化抑制逆转录转座子的转录。在小鼠胚胎干细胞（ESCs）中，组蛋白H3赖氨酸9甲基化（H3K9me）在抑制内源性逆转录病毒（erv）中起着至关重要的作用，其中一些病毒在转位时仍然活跃。尽管人类erv （herv）对转位不活跃，但它们中的许多仍然具有转录活性，并且herv的再激活与细胞类型特异性基因表达或肿瘤发生有关。为了阐明包括H3K9me在内的组蛋白甲基化如何对herv的抑制至关重要，我们试图建立缺乏H3K9甲基转移酶SETDB1的人类iPS/ES细胞。利用CRISPR/Cas9和引导RNA系统，我们证实了SETDB1可以被该系统破坏。一旦我们在人类iPS细胞中获得条件SETDB1，我们将分析SETDB1如何调节herv的转录，以及SETDB1如何对人类其他类型的反转录转座子的沉默至关重要。

It is well known that DNA methylation and histone methylation suppress transcription of retrotransposons. In mouse embryonic stem cells (ESCs), histone H3 lysine 9 methylation (H3K9me) plays crucial roles for repression of endogenous retroviruses (ERVs), some of which are still active for transposition. Although human ERVs (HERVs) are not active for transposition, many of them are still transcriptionally active and reactivation of HERVs is linked with cell type specific gene expression or tumorigenesis. To elucidate how histone methylation including H3K9me is crucial for repression of HERVs, we tried to establish human iPS/ES cells deficient for H3K9 methyltransferase SETDB1. Using the CRISPR/Cas9 and guide RNA system, we confirmed that SETDB1 can be disrupted by the system. Once we obtain conditional SETDB1 KO human iPS cells, we would like to analyze how transcription of HERVs is regulated by SETDB1 and how SETDB1 is crucial for silencing of other types of retrotransposons in human.