Skaar Jeffrey R, Ferris Andrea L, Wu Xiaolin, Saraf Anita, Khanna Kum Kum, Florens Laurence, Washburn Michael P, Hughes Stephen H, Pagano Michele
Department of Pathology, Laura and Isaac Perlmutter Cancer Center, New York University School of Medicine, 522 First Avenue, New York, NY 10016, USA.
HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA.
Cell Res. 2015 Mar;25(3):288-305. doi: 10.1038/cr.2015.19. Epub 2015 Feb 13.
Complexes containing INTS3 and either NABP1 or NABP2 were initially characterized in DNA damage responses, but their biochemical function remained unknown. Using affinity purifications and HIV Integration targeting-sequencing (HIT-Seq), we find that these complexes are part of the Integrator complex, which binds RNA Polymerase II and regulates specific target genes. Integrator cleaves snRNAs as part of their processing to their mature form in a mechanism that is intimately coupled with transcription termination. However, HIT-Seq reveals that Integrator also binds to the 3' end of replication-dependent histones and promoter proximal regions of genes with polyadenylated transcripts. Depletion of Integrator subunits results in transcription termination failure, disruption of histone mRNA processing, and polyadenylation of snRNAs and histone mRNAs. Furthermore, promoter proximal binding of Integrator negatively regulates expression of genes whose transcripts are normally polyadenylated. Integrator recruitment to all three gene classes is DSIF-dependent, suggesting that Integrator functions as a termination complex at DSIF-dependent RNA Polymerase II pause sites.
最初在DNA损伤反应中对包含INTS3以及NABP1或NABP2的复合物进行了表征，但其生化功能仍然未知。通过亲和纯化和HIV整合靶向测序（HIT-Seq），我们发现这些复合物是整合酶复合物的一部分，该复合物与RNA聚合酶II结合并调节特定的靶基因。整合酶在snRNA加工成成熟形式的过程中切割snRNA，其机制与转录终止密切相关。然而，HIT-Seq显示整合酶还与复制依赖性组蛋白的3'末端以及具有聚腺苷酸化转录本的基因的启动子近端区域结合。整合酶亚基的缺失导致转录终止失败、组蛋白mRNA加工中断以及snRNA和组蛋白mRNA的聚腺苷酸化。此外，整合酶在启动子近端的结合会负调节其转录本通常进行聚腺苷酸化的基因的表达。整合酶被招募到所有三类基因上均依赖于DSIF，这表明整合酶在依赖于DSIF的RNA聚合酶II暂停位点处作为终止复合物发挥作用。
