Identification and Characterization of Bmi-1-responding Element within the Human p16 Promoter
Identification and Characterization of Bmi-1-responding Element within the Human p16 Promoter
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人 p16 启动子内 Bmi-1 响应元件的鉴定和表征
DOI：
10.1074/jbc.m110.133686
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发表时间：
2010-10-22
影响因子：
4.8
通讯作者：
Lu, Zhigang
中科院分区：
文献类型：
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作者：
Meng, Sha;Luo, Min;Lu, Zhigang
Bmi-1是第一个功能鉴定的多梳基因家族成员，在细胞周期调控、细胞永生化、细胞衰老等过程中发挥重要作用。BMI-1参与癌症的发生和发展，是癌症治疗的有效靶点。BMI-1调控的一个重要途径是涉及p16(INK4a)和p19(Arf)这两个细胞周期蛋白依赖的激酶抑制剂，因为BMI-1抑制了它们编码的INK4a基因。Bmi-1的上调与p16的下调在多种肿瘤中都有密切的相关性，但Bmi-1如何调控p16的表达尚不清楚。在本研究中，我们揭示了BMI-1通过直接与p16启动子中的BMI-1反应元件(BRE)结合来调节p16的表达。BRE位于p16ATG密码子上游的-821~-732位。BRE本身就足以允许BMI-1介导的CMV启动子的调节。Bmi-1通常通过与Ring2形成复合体发挥作用；然而，p16的调节独立于Ring2。对BMI-1沉淀的染色质DNA进行染色质免疫沉淀测序，发现BMI-1靶向1536个基因，包括与组织特异性分化、细胞周期和细胞凋亡相关的基因。通过分析这些基因的结合序列，我们发现了两个高度保守的BMI-1结合基序，这两个基序是BMI-1介导的p16启动子调控所必需的。综上所述，我们的结果揭示了Bmi-1介导的p16基因调控的分子机制，从而为进一步了解Bmi-1的功能提供了一个敏感的高通量平台，用于筛选Bmi-1靶向癌症治疗的小分子。
Bmi-1, the first functionally identified polycomb gene family member, plays critical roles in cell cycle regulation, cell immortalization, and cell senescence. Bmi-1 is involved in the development and progression of carcinomas and is a potent target for cancer therapy. One important pathway regulated by Bmi-1 is that involving two cyclin-dependent kinase inhibitors, p16(Ink4a) and p19(Arf), as Bmi-1 represses the INK4a locus on which they are encoded. A close correlation between the up-regulation of Bmi-1 and down-regulation of p16 has been demonstrated in various tumors; however, how Bmi-1 regulates p16 expression is not clear. In this study, we revealed that Bmi-1 regulates the expression of p16 by binding directly to the Bmi-1-responding element (BRE) within the p16 promoter. The BRE resided at bp -821 to -732 upstream of the p16 ATG codon. BRE alone was sufficient to allow Bmi-1-mediated regulation of the CMV promoter. Bmi-1 typically functions by forming a complex with Ring2; however, regulation of p16 was independent of Ring2. Chromatin immunoprecipitation sequencing of Bmi-1-precipitated chromatin DNA revealed that 1536 genes were targeted by Bmi-1, including genes involved in tissue-specific differentiation, cell cycle, and apoptosis. By analyzing the binding sequences of these genes, we found two highly conserved Bmi-1-binding motifs, which were required for Bmi-1-mediated p16 promoter regulation. Taken together, our results revealed the molecular mechanism of Bmi-1-mediated regulation of the p16 gene, thus providing further insights into the functions of Bmi-1 as well as a sensitive high-throughput platform with which to screen Bmi-1-targeted small molecules for cancer therapy.