Reja Rohit, Vinayachandran Vinesh, Ghosh Sujana, Pugh B Franklin
Center for Eukaryotic Gene Regulation, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Genes Dev. 2015 Sep 15;29(18):1942-54. doi: 10.1101/gad.268896.115.
The 137 ribosomal protein genes (RPGs) of Saccharomyces provide a model for gene coregulation. We examined the positional and functional organization of their regulators (Rap1 [repressor activator protein 1], Fhl1, Ifh1, Sfp1, and Hmo1), the transcription machinery (TFIIB, TFIID, and RNA polymerase II), and chromatin at near-base-pair resolution using ChIP-exo, as RPGs are coordinately reprogrammed. Where Hmo1 is enriched, Fhl1, Ifh1, Sfp1, and Hmo1 cross-linked broadly to promoter DNA in an RPG-specific manner and demarcated by general minor groove widening. Importantly, Hmo1 extended 20-50 base pairs (bp) downstream from Fhl1. Upon RPG repression, Fhl1 remained in place. Hmo1 dissociated, which was coupled to an upstream shift of the +1 nucleosome, as reflected by the Hmo1 extension and core promoter region. Fhl1 and Hmo1 may create two regulatable and positionally distinct barriers, against which chromatin remodelers position the +1 nucleosome into either an activating or a repressive state. Consistent with in vitro studies, we found that specific TFIID subunits, in addition to cross-linking at the core promoter, made precise cross-links at Rap1 sites, which we interpret to reflect native Rap1-TFIID interactions. Our findings suggest how sequence-specific DNA binding regulates nucleosome positioning and transcription complex assembly >300 bp away and how coregulation coevolved with coding sequences.
酿酒酵母的137个核糖体蛋白基因(RPGs)为基因协同调控提供了一个模型。我们使用ChIP-exo技术,以近碱基对分辨率研究了其调控因子(Rap1[阻遏激活蛋白1]、Fhl1、Ifh1、Sfp1和Hmo1)、转录机制(TFIIB、TFIID和RNA聚合酶II)以及染色质的位置和功能组织,因为RPGs是协同重编程的。在Hmo1富集的地方,Fhl1、Ifh1、Sfp1和Hmo1以RPG特异性方式广泛交联到启动子DNA上,并由一般的小沟变宽来界定。重要的是,Hmo1从Fhl1下游延伸20 - 50个碱基对(bp)。在RPG抑制时,Fhl1保持原位。Hmo1解离,这与+1核小体的上游移位相关,如Hmo1延伸和核心启动子区域所反映的那样。Fhl1和Hmo1可能形成两个可调控且位置不同的屏障,染色质重塑因子将+1核小体定位在这两个屏障上,使其处于激活或抑制状态。与体外研究一致,我们发现特定的TFIID亚基除了在核心启动子处交联外,还在Rap1位点进行精确交联,我们将其解释为反映天然的Rap1 - TFIID相互作用。我们的研究结果表明了序列特异性DNA结合如何调控300 bp以外的核小体定位和转录复合物组装,以及协同调控如何与编码序列共同进化。