Closed chromatin architecture is induced by an RNA duplex targeting the HIV-1 promoter region.
Closed chromatin architecture is induced by an RNA duplex targeting the HIV-1 promoter region.
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DOI：
10.1074/jbc.m709651200
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发表时间：
2008-08-22
期刊：
影响因子：
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通讯作者：
Kelleher AD
中科院分区：
文献类型：
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作者：
Suzuki K;Juelich T;Lim H;Ishida T;Watanebe T;Cooper DA;Rao S;Kelleher AD
在一些哺乳动物系统中，靶向基因启动子区中的同源序列的小干扰RNA（siRNA）诱导转录基因沉默（TGS）。我们先前已经报道了通过靶向人免疫缺陷病毒1型（HIV-1）启动子区域内的串联NF-κ B结合基序的siRNA（prom-A siRNA）诱导TGS。在这里，我们报告说，诱导TGS的prom-A siRNA是伴随着立即和持续的Argonaute-1（Ago 1），组蛋白脱乙酰酶-1（HDAC 1），并诱导组蛋白3的二甲基化赖氨酸9（H3 K9 me 2），已知的过程与转录沉默。H3 K9 me 2和HDAC 1水平升高扩散到靶序列上游，H3 K9 me 2水平升高也扩散到编码区下游。此外，这种siRNA诱导HIV-1转录起始位点区域中DNA对限制性酶消化的可及性的立即改变。这种可接近性的变化是由于已知与整合的前病毒的该区域相关的核小体的重新定位。尽管理论上存在这样的可能性：观察到的病毒抑制可以由PTGS机制介导，其中该SiRNA作用于病毒的3 ®长期重复序列，但我们证明该SiRNA和其他三种U3靶向SiRNA是低效的诱导剂PTGS。这些数据有力地表明，靶向启动子区域的siRNA主要在HIV的5 ®-长期重复内的位点起作用，以诱导转录沉默和HIV启动子区域的染色质结构的改变，其延伸远远超过直接siRNA靶位点。这些诱导的变化与潜伏性HIV-1感染中描述的变化一致。
In some mammalian systems small interfering RNAs (siRNA) targeting homologous sequences in promoter regions of genes induce transcriptional gene silencing (TGS). We have previously reported the induction of TGS by an siRNA (prom-A siRNA) targeting the tandem NF-κB-binding motifs within the human immunodeficiency virus, type 1 (HIV-1), promoter region. Here we report that induction of TGS by prom-A siRNA is accompanied by immediate and sustained local recruitment of Argonaute-1 (Ago1), histone deacetylase-1 (HDAC1), and induction of dimethylation of histone 3 at lysine 9 (H3K9me2), processes known to be associated with transcriptional silencing. Elevated levels of H3K9me2 and HDAC1 spread upstream of the target sequence, and elevated H3K9me2 levels also spread downstream into the coding region. Moreover, this siRNA induces an immediate change in DNA accessibility to restriction enzyme digestion in the region of the transcription initiation site of the HIV-1. This change in accessibility is because of the relocation of a nucleosome known to be associated with this region of the integrated pro-virus. Although there is a theoretical possibility that the observed viral suppression could be mediated by the PTGS mechanism with this siRNA acting at the 3 ®-long term repeat of the virus, we demonstrate that this siRNA, and three other U3 targeted siRNAs, are inefficient inducers of PTGS. These data strongly suggest that siRNA targeting the promoter region acts predominantly at a site within the 5 ®-long term repeat of HIV to induce transcriptional silencing and alterations to chromatin structure of the HIV promoter region that extend well beyond the immediate siRNA target site. These induced changes are consistent with those described in latent HIV-1 infection.