HDIR1参与基因转录抑制的机制研究

In mammals, 70%-80% CpG sequences of the whole genome are methylated. CpG methylation in gene regulatory regions is generally associated with transcriptional repression. This mechnism is correlated with many biological processes and involved in the development of many diseases. The mechanisms of how DNA methylation could repress transcription have been extensively explored by many groups. The widly-accepted model currently suggests that DNA methylatin could be recognized by specific methylated-CpG binder such as MeCP2 and MBD family proteins. These proteins could then recruit histone deacetylases and chromatin remodelers to mediate gene silencing. However, some researches found that histone deacetylase inhibitors alone could not induce all DNA-methylation-silenced genes. These data suggests that their might be some unknown pathways, which are independent of histone deactyltion, involved in the repression of DNA methylated genes. We established a stable cell line with an artificially methylated EGFP reporter which could be activated by 5-Aza (DNMT inhibitor) but not by TSA (histone actylase inhibitor). We performed a high-throughput RNAi screen with this cell line and found some candidte genes, which could activate the reporter when down-regulated. Within the candidates list, we found a gene, we termed HDIR1, knocking down of which could activate the reporter. Interestingly, we found that the upregulated gene upon HDIR1 knockdown are those active transcribing genes. Furthermore, we found that HDIR1 could regulate the transcription of enhance RNA (eRNA). We plan to further study the mechanism of HDIR1 on transcription.

在哺乳动物的基因组中DNA甲基化与多种生物学现象和多种疾病的发生相关。目前其公认的机制是一些能够特异识别甲基化CpG的蛋白被甲基化的染色质DNA招募并进而招募组蛋白去乙酰化酶和染色质重塑因子来介导基因沉默。但是，一些研究却发现即使抑制组蛋白去乙酰化酶的活性，依然有一部分被DNA甲基化抑制的基因无法激活。这些研究说明可能DNA甲基化抑制基因表达还存在不依赖于组蛋白去乙酰化酶的新通路。我们将人为甲基化的报告基因插入HEK293F细胞基因组中并用其进行了高通量的RNAi 筛选，找到了一些敲低后可以激活报告基因的候选基因。我们发现了一个前人未有深入研究的基因HDIR1。敲除该基因可以很好地激活报告基因。有趣的是，我们发现敲低HIDR1后，转录激活的主要是那些本已活跃转录的基因。另外，我们还发现HDIR1能够调控增强子RNA的转录。因此我们计划深入HDIR1对转录调控机制。