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首页> 外文期刊>Molecular and Cellular Biology >Trf4 and Trf5 Proteins of Saccharomyces cerevisiae Exhibit Poly(A) RNA Polymerase Activity but No DNA Polymerase Activity
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Trf4 and Trf5 Proteins of Saccharomyces cerevisiae Exhibit Poly(A) RNA Polymerase Activity but No DNA Polymerase Activity

机译：酿酒酵母的Trf4和Trf5蛋白具有Poly（A）RNA聚合酶活性，但无DNA聚合酶活性

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The Saccharomyces cerevisiae Trf4 and Trf5 proteins are members of a distinct family of eukaryotic DNA polymerase β-like nucleotidyltransferases, and a template-dependent DNA polymerase activity has been reported for Trf4. To define the nucleotidyltransferase activities associated with Trf4 and Tr5, we purified these proteins from yeast cells and show that whereas both proteins exhibit a robust poly(A) polymerase activity, neither of them shows any evidence of a DNA polymerase activity. The poly(A) polymerase activity, as determined for Trf4, is strictly Mn2+ dependent and highly ATP specific, incorporating AMP onto the free 3′-hydroxyl end of an RNA primer. Unlike the related poly(A) polymerases from other eukaryotes, which are located in the cytoplasm and regulate the stability and translation efficiency of specific mRNAs, the Trf4 and Trf5 proteins are nuclear, and a multiprotein complex associated with Trf4 has been recently shown to polyadenylate a variety of misfolded or inappropriately expressed RNAs which activate their degradation by the exosome. To account for the effects of Trf4/Trf5 proteins on the various aspects of DNA metabolism, including chromosome condensation, DNA replication, and sister chromatid cohesion, we suggest an additional and essential role for the Trf4 and Trf5 protein complexes in generating functional mRNA poly(A) tails in the nucleus.
机译：酿酒酵母Trf4和Trf5蛋白是真核DNA聚合酶β样核苷酸转移酶家族的成员，Trf4具有依赖模板的DNA聚合酶活性。为了定义与Trf4和Tr5相关的核苷酸转移酶活性，我们从酵母细胞中纯化了这些蛋白，结果表明，尽管这两种蛋白均显示出强大的poly（A）聚合酶活性，但它们均未显示出DNA聚合酶活性的任何证据。根据Trf4的测定，poly（A）聚合酶活性严格依赖Mn 2 + 且具有高度ATP特异性，可将AMP掺入RNA引物的游离3'-羟基末端。与位于细胞质中并调节特定mRNA的稳定性和翻译效率的其他真核生物相关的poly（A）聚合酶不同，Trf4和Trf5蛋白是有核的，与Trf4相关的多蛋白复合物最近已显示出聚腺苷酸各种错误折叠或表达不当的RNA，它们会通过外来体激活其降解。为了说明Trf4 / Trf5蛋白对DNA代谢各个方面的影响，包括染色体浓缩，DNA复制和姐妹染色单体凝聚力，我们建议Trf4和Trf5蛋白复合物在产生功能性mRNA poly（ A）尾巴在细胞核中。

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