Ribosomal RNA Gene Transcription Mediated by the Master Genome Regulator Protein CCCTC-binding Factor (CTCF) Is Negatively Regulated by the Condensin Complex
Ribosomal RNA Gene Transcription Mediated by the Master Genome Regulator Protein CCCTC-binding Factor (CTCF) Is Negatively Regulated by the Condensin Complex
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由主基因组调节蛋白 CCCTC 结合因子 (CTCF) 介导的核糖体 RNA 基因转录受到凝缩蛋白复合物的负调节
DOI：
10.1074/jbc.m113.486175
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发表时间：
2013-09-06
影响因子：
4.8
通讯作者：
Yao, Hongjie
中科院分区：
文献类型：
--
作者：
Huang, Kaimeng;Jia, Jinping;Yao, Hongjie
CCCTC结合因子（CTCF）是普遍表达的“编织大师”，在基因组中发挥多种功能，包括转录激活/抑制、染色质绝缘、印记、X染色体失活和高阶染色质组织。研究表明，CTCF 有助于将上游结合因子招募到核糖体 DNA (rDNA) 上，并调节 rDNA 重复序列的局部表观遗传状态。然而，CTCF调节rRNA基因转录的机制尚不清楚。在这里，我们发现野生型 CTCF 增强了宫颈癌细胞中的前 rRNA 水平、细胞大小和细胞生长。相反，RNA 干扰介导的 CTCF 敲除减少了前 rRNA 转录。 CTCF 以 RNA 聚合酶 I 依赖性方式正向调节 rRNA 基因转录。我们将 RRGR 基序确定为 CTCF C 末端区域的假定核仁定位序列，是激活 rRNA 基因转录所需的。使用质谱法，我们鉴定了 SMC2 和 SMC4，这是与 CTCF 相互作用的凝缩蛋白复合物的两个亚基。 Condensin 负向调节 CTCF 介导的 rRNA 基因转录。 SMC2 表达的敲低显着促进 CTCF 和上游结合因子加载到 rDNA 位点上，并增加 rDNA 位点上的组蛋白乙酰化。综上所述，我们的研究表明，凝缩蛋白与 CTCF 竞争结合特定的 rDNA 位点，并对 CTCF 介导的 rRNA 基因转录进行负调控。
CCCTC-binding factor (CTCF) is a ubiquitously expressed "master weaver" and plays multiple functions in the genome, including transcriptional activation/repression, chromatin insulation, imprinting, X chromosome inactivation, and high-order chromatin organization. It has been shown that CTCF facilitates the recruitment of the upstream binding factor onto ribosomal DNA (rDNA) and regulates the local epigenetic state of rDNA repeats. However, the mechanism by which CTCF modulates rRNA gene transcription has not been well understood. Here we found that wild-type CTCF augments the pre-rRNA level, cell size, and cell growth in cervical cancer cells. In contrast, RNA interference-mediated knockdown of CTCF reduced pre-rRNA transcription. CTCF positively regulates rRNA gene transcription in a RNA polymerase I-dependent manner. We identified an RRGR motif as a putative nucleolar localization sequence in the C-terminal region of CTCF that is required for activating rRNA gene transcription. Using mass spectrometry, we identified SMC2 and SMC4, two subunits of condensin complexes that interact with CTCF. Condensin negatively regulates CTCF-mediated rRNA gene transcription. Knockdown of SMC2 expression significantly facilitates the loading of CTCF and the upstream binding factor onto the rDNA locus and increases histone acetylation across the rDNA locus. Taken together, our study suggests that condensin competes with CTCF in binding to a specific rDNA locus and negatively regulates CTCF-mediated rRNA gene transcription.