The Ccr4-Not Deadenylase Subunits CNOT7 and CNOT8 Have Overlapping Roles and Modulate Cell Proliferation
The Ccr4-Not Deadenylase Subunits CNOT7 and CNOT8 Have Overlapping Roles and Modulate Cell Proliferation
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DOI：
10.1091/mbc.e09-02-0146
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发表时间：
2009-09-01
影响因子：
3.3
通讯作者：
Winkler, G. Sebastiaan
中科院分区：
文献类型：
--
作者：
Aslam, Akhmed;Mittal, Saloni;Winkler, G. Sebastiaan
准确的基因表达需要对mRNA水平的精确控制，这是由核(前)mRNA合成和加工的相对速率以及细胞质mRNA的周转决定的。MRNA降解的一个关键步骤是去除聚(A)尾，这涉及几种死烯基酶，包括CCR4-NOT复合体的成分。在这里，我们重点研究了人类类似物Cnot7(hCaf1/Caf1a)和CNOT8(hPop2/Caf1b/Calif)的作用，它们具有由DEDD核酶结构域介导的死烯基酶活性。我们发现，有效的增殖需要这两个亚基，尽管Cnot7和CNOT8的联合敲除进一步减少了细胞增殖，表明这些蛋白质之间存在部分冗余。有趣的是，Cnot7在细胞增殖中的作用部分依赖于它的催化活性。另一方面，Cnot7和BTG2之间的相互作用似乎对MCF7细胞的增殖不那么重要，这表明Cnot7并不是单独与BTG2一起发挥作用。BTG2是参与转录和mRNA衰退的抗增殖BTG/Tob家族的成员。进一步分析Cnot7和/或CNOT8基因敲除细胞的基因表达谱，强调了这些亚基之间的部分冗余，并表明CCR4-NOT复合体对几个基因的调控，包括抑制抗增殖基因MSMB和PMP22，有助于细胞增殖。
Accurate gene expression requires the precise control of mRNA levels, which are determined by the relative rates of nuclear (pre-) mRNA synthesis and processing, and cytoplasmic mRNA turnover. A key step in mRNA degradation is the removal of the poly(A) tail, which involves several deadenylases including components of the Ccr4-Not complex. Here, we focused on the role of the human paralogues CNOT7 (hCaf1/Caf1a) and CNOT8 (hPop2/Caf1b/Calif), which possess deadenylase activity mediated by DEDD nuclease domains. We show that efficient proliferation requires both subunits, although combined knockdown of CNOT7 and CNOT8 further reduces cell proliferation indicating partial redundancy between these proteins. Interestingly, the function of CNOT7 in cell proliferation partly depends on its catalytic activity. On the other hand, the interaction between CNOT7 and BTG2, a member of the antiproliferative BTG/Tob family involved in transcription and mRNA decay appears less important for proliferation of MCF7 cells, suggesting that CNOT7 does not function solely in conjunction with BTG2. Further analysis of gene expression profiles of CNOT7 and/or CNOT8 knockdown cells underscores the partial redundancy between these subunits and suggests that regulation of several genes, including repression of the antiproliferative genes MSMB and PMP22, by the Ccr4-Not complex contributes to cell proliferation.