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首页> 外文期刊>Nucleic Acids Research >Saccharomyces cerevisiae Mre11 is a high-affinity G4 DNA-binding protein and a G-rich DNA-specific endonuclease: implications for replication of telomeric DNA.
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Saccharomyces cerevisiae Mre11 is a high-affinity G4 DNA-binding protein and a G-rich DNA-specific endonuclease: implications for replication of telomeric DNA.

机译：酿酒酵母Mre11是一种高亲和力的G4 DNA结合蛋白和一种富含G的DNA特异性核酸内切酶：对端粒DNA复制的影响。

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摘要

In Saccharomyces cerevisiae, Mre11p/Rad50p/Xrs2p (MRX) complex plays a vital role in several nuclear processes including cellular response to DNA damage, telomere length maintenance, cell cycle checkpoint control and meiotic recombination. Telomeres are comprised of tandem repeats of G-rich DNA and are incorporated into non-nucleosomal chromatin. Although the structure of the yeast telomeric DNA is poorly understood, it has been suggested that the G-rich sequences can fold into G4 DNA, which has been shown to inhibit DNA synthesis by telomerase. However, little is known about the factors and mechanistic aspects of the generation of appropriate termini for DNA synthesis by telomerase. Here, we show that S.cerevisiae Mre11 protein (ScMre11p) possesses substantially higher binding affinity for G4 DNA, over single- or double-stranded DNA, and binding was inhibited by poly(dG) or porphyrin. Binding of ScMre11p to G4 DNA was most robust, compared with G2' DNA and the resulting protein-DNA complexes were strikingly very resistant to dissociation by NaCl. Remarkably, binding of ScMre11p to G4 DNA and G-rich single-stranded DNA was accompanied by the endonucleolytic cleavage at sites flanking the array of G residues and G-quartets in Mn2+-dependent manner. Collectively, these results suggest that ScMre11p is likely to play a major role in generating appropriate substrates for DNA synthesis by telomerase and telomere-binding proteins. We discuss the implications of these findings with regard to telomere length maintenance by telomerase-dependent and independent mechanisms.
机译：在酿酒酵母中，Mre11p / Rad50p / Xrs2p（MRX）复合体在包括细胞对DNA损伤的反应，端粒长度维持，细胞周期检查点控制和减数分裂重组在内的几个核过程中起着至关重要的作用。端粒由富含G的DNA的串联重复序列组成，并掺入非核小体的染色质中。尽管对酵母端粒DNA的结构了解甚少，但已表明富含G的序列可折叠成G4 DNA，已显示抑制端粒酶合成DNA。但是，关于端粒酶合成DNA的合适末端的因素和机理方面知之甚少。在这里，我们显示酿酒酵母Mre11蛋白（ScMre11p）具有比单链或双链DNA更高的对G4 DNA的结合亲和力，并且结合被聚（dG）或卟啉抑制。与G2'DNA相比，ScMre11p与G4 DNA的结合最牢固，并且所得的蛋白质-DNA复合物对NaCl的解离具有非常强的抵抗力。值得注意的是，ScMre11p与G4 DNA和富含G的单链DNA的结合伴随着以Mn2 +依赖性方式在G残基和G四元组阵列两侧的位点进行了核酸内切酶裂解。总体而言，这些结果表明，ScMre11p在端粒酶和端粒结合蛋白产生合适的DNA合成底物中可能起主要作用。我们讨论端粒酶依赖和独立机制端粒长度维持这些发现的含义。

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