Lau Nga-Chi, Kolkman Annemieke, van Schaik Frederik M A, Mulder Klaas W, Pijnappel W W M Pim, Heck Albert J R, Timmers H Th Marc
Department of Physiological Chemistry, University Medical Center Utrecht, Utrecht, The Netherlands.
Biochem J. 2009 Aug 27;422(3):443-53. doi: 10.1042/BJ20090500.
The Ccr4-Not complex is evolutionarily conserved and important for regulation of mRNA synthesis and decay. The composition of the yeast complex has been well described. Orthologues of the yeast Ccr4-Not components have been identified in human cells including multiple subunits with mRNA deadenylase activity. In the present study, we examine the composition of the human Ccr4-Not complex in an in-depth proteomic approach using stable cell lines expressing tagged CNOT proteins. We find at least four different variants of the human complex, consisting of seven stable core proteins and mutually exclusive associated mRNA deadenylase subunits. Interestingly, human CNOT4 is in a separate approximately 200 kDa complex. Furthermore, analyses of associated proteins indicate involvement of Ccr4-Not complexes in splicing, transport and localization of RNA molecules. Taken together, human Ccr4-Not complexes are heterogeneous in composition owing to differences in their deadenylase subunits, which may reflect the multi-functionality of these complexes in cellular processes.
Ccr4-Not复合物在进化上是保守的，对mRNA的合成和降解调控至关重要。酵母复合物的组成已得到充分描述。在人类细胞中已鉴定出酵母Ccr4-Not组分的直系同源物，包括具有mRNA去腺苷酸化酶活性的多个亚基。在本研究中，我们使用表达标记的CNOT蛋白的稳定细胞系，通过深入的蛋白质组学方法研究人类Ccr4-Not复合物的组成。我们发现人类复合物至少有四种不同变体，由七种稳定的核心蛋白和相互排斥的相关mRNA去腺苷酸化酶亚基组成。有趣的是，人类CNOT4存在于一个单独的约200 kDa复合物中。此外，对相关蛋白的分析表明Ccr4-Not复合物参与RNA分子的剪接、转运和定位。综上所述，由于去腺苷酸化酶亚基的差异，人类Ccr4-Not复合物在组成上是异质的，这可能反映了这些复合物在细胞过程中的多功能性。
