期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：44
页码：15622-15629
DOI：10.1073/pnas.1416858111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceArgonaute proteins are well characterized factors in posttranscriptional gene silencing, the process by which small RNAs trigger mRNA degradation or inhibit translation in the cytoplasm. We report here that Argonaute proteins also play important roles in the nucleus. Our genome-wide analysis reveals that Argonaute-1 (AGO-1) binds preferentially to active transcriptional enhancers and that this association is mediated by the RNAs that are transcribed from these enhancers (eRNAs). Moreover, the interaction of AGO-1 with enhancers does not seem to regulate transcription of the neighboring genes but of alternative and constitutive splicing. These results contribute to the understanding of the complex regulation of gene expression in eukaryotic cells. The roles of Argonaute proteins in cytoplasmic microRNA and RNAi pathways are well established. However, their implication in small RNA-mediated transcriptional gene silencing in the mammalian cell nucleus is less understood. We have recently shown that intronic siRNAs cause chromatin modifications that inhibit RNA polymerase II elongation and modulate alternative splicing in an Argonaute-1 (AGO1)-dependent manner. Here we used chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) to investigate the genome-wide distribution of AGO1 nuclear targets. Unexpectedly, we found that about 80% of AGO1 clusters are associated with cell-type-specific transcriptional enhancers, most of them (73%) overlapping active enhancers. This association seems to be mediated by long, rather than short, enhancer RNAs and to be more prominent in intragenic, rather than intergenic, enhancers. Paradoxically, crossing ChIP-seq with RNA-seq data upon AGO1 depletion revealed that enhancer-bound AGO1 is not linked to the global regulation of gene transcription but to the control of constitutive and alternative splicing, which was confirmed by an individual gene analysis explaining how AGO1 controls inclusion levels of the cassette exon 107 in the SYNE2 gene.
关键词：Argonaute proteins ; transcriptional enhancers ; alternative splicing
