Department of Biochemistry 1, Hamamatsu University School of Medicine, Shizuoka, Japan.
Oncogene. 2011 Apr 21;30(16):1956-62. doi: 10.1038/onc.2010.568. Epub 2010 Dec 13.
A 42 kb region on human chromosome 9p21 encodes for three distinct tumor suppressors, p16(INK4A), p14(ARF) and p15(INK4B), and is altered in an estimated 30-40% of human tumors. The expression of the INK4A-ARF-INK4B gene cluster is silenced by polycomb during normal cell growth and is activated by oncogenic insults and during aging. How the polycomb is recruited to repress this gene cluster is unclear. Here, we show that expression of oncogenic Ras, which stimulates the expression of p15(INK4B) and p16(INK4A), but not p14(ARF), inhibits the expression of ANRIL (antisense non-coding RNA in the INK4 locus), a 3.8 kb-long non-coding RNA expressed in the opposite direction from INK4A-ARF-INK4B. We show that the p15(INK4B) locus is bound by SUZ12, a component of polycomb repression complex 2 (PRC2), and is H3K27-trimethylated. Notably, depletion of ANRIL disrupts the SUZ12 binding to the p15(INK4B) locus, increases the expression of p15(INK4B), but not p16(INK4A) or p14(ARF), and inhibits cellular proliferation. Finally, RNA immunoprecipitation demonstrates that ANRIL binds to SUZ12 in vivo. Collectively, these results suggest a model in which ANRIL binds to and recruits PRC2 to repress the expression of p15(INK4B) locus.
9p21 号人类染色体上的一个 42kb 区域编码三个不同的肿瘤抑制因子，p16(INK4A)、p14(ARF)和 p15(INK4B)，并且在大约 30-40%的人类肿瘤中发生改变。在正常细胞生长过程中，多梳抑制复合物（polycomb）沉默 INK4A-ARF-INK4B 基因簇的表达，并且在致癌因素和衰老时被激活。多梳复合物如何被招募来抑制这个基因簇尚不清楚。在这里，我们发现致癌性 Ras 的表达，其刺激 p15(INK4B)和 p16(INK4A)的表达，但不刺激 p14(ARF)的表达，会抑制 3.8kb 长的反义非编码 RNA ANRIL（INK4 基因座中的反义非编码 RNA）的表达，该 RNA 从 INK4A-ARF-INK4B 的相反方向表达。我们发现 p15(INK4B)基因座被 SUZ12 结合，SUZ12 是多梳抑制复合物 2（PRC2）的一个组成部分，并且 H3K27 被三甲基化。值得注意的是，ANRIL 的耗竭会破坏 SUZ12 与 p15(INK4B)基因座的结合，增加 p15(INK4B)的表达，但不增加 p16(INK4A)或 p14(ARF)的表达，并抑制细胞增殖。最后，RNA 免疫沉淀证明 ANRIL 在体内与 SUZ12 结合。总之，这些结果表明了一个模型，即 ANRIL 结合并招募 PRC2 来抑制 p15(INK4B)基因座的表达。
