Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA.
Nucleic Acids Res. 2011 Mar;39(6):2188-209. doi: 10.1093/nar/gkq1029. Epub 2010 Nov 12.
The cap-binding complex (CBC) binds to the cap structure of mRNA to protect it from exonucleases as well as to regulate downstream post-transcriptional events, translational initiation and nonsense-mediated mRNA decay. However, its role in regulation of the upstream transcriptional events such as initiation or elongation remains unknown. Here, using a formaldehyde-based in vivo cross-linking and chromatin immunoprecipitation assay in conjunction with transcriptional, mutational and co-immunoprecipitational analyses, we show that CBC is recruited to the body of yeast gene, and then stimulates the formation of pre-initiation complex (PIC) at several yeast promoters through its interaction with Mot1p (modifier of transcription). Mot1p is recruited to these promoters, and enhances the PIC formation. We find that CBC promotes the recruitment of Mot1p which subsequently stimulates PIC formation at these promoters. Furthermore, the formation of PIC is essential for recruitment of CBC. Thus, our study presents an interesting observation that an mRNA binding factor exhibits a reciprocal synergistic effect on formation of PIC (and hence transcriptional initiation) at the promoter, revealing a new pathway of eukaryotic gene regulation in vivo.
帽结合复合物（CBC）与 mRNA 的帽结构结合，以保护其免受核酸外切酶的侵害，并调节下游的转录后事件、翻译起始和无意义介导的 mRNA 降解。然而，其在调节上游转录事件（如起始或延伸）中的作用尚不清楚。在这里，我们使用基于甲醛的体内交联和染色质免疫沉淀测定，结合转录、突变和共免疫沉淀分析，表明 CBC 被招募到酵母基因的主体中，然后通过与 Mot1p（转录修饰因子）相互作用，刺激几个酵母启动子中起始前复合物（PIC）的形成。Mot1p 被招募到这些启动子上，并增强 PIC 的形成。我们发现，CBC 促进 Mot1p 的招募，随后刺激这些启动子上的 PIC 形成。此外，PIC 的形成对于 CBC 的招募是必不可少的。因此，我们的研究提出了一个有趣的观察结果，即一种 mRNA 结合因子在启动子处对 PIC（进而对转录起始）的形成表现出相互协同的效应，揭示了真核生物基因在体内调节的新途径。
