Ku binds telomeric DNA in vitro
Ku binds telomeric DNA in vitro
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DOI：
10.1074/jbc.274.30.21223
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发表时间：
1999-07-23
影响因子：
4.8
通讯作者：
de Lange, T
中科院分区：
文献类型：
--
作者：
Bianchi, A;de Lange, T
Ku 是一种异二聚体蛋白，对双链 DNA 的末端、切口和缺口具有高结合亲和力。在哺乳动物细胞和芽殖酵母中，Ku 在双链断裂修复途径的非同源末端连接中发挥作用。然而，与酵母相比，Ku 在哺乳动物细胞 DNA 修复中发挥着更重要的作用，其中同源依赖性途径是主要途径。最近，Ku 已被证明是酵母中端粒复合物的一个可能组成部分，这表明 Ku 在哺乳动物端粒中可能具有类似的作用。然而，富含 G 的长单链突出持续存在于哺乳动物中，但不存在于酵母端粒中。这些突出端有可能在体外折叠成 G-G 碱基对构象，例如 G-四联体，这可能会阻止 Ku 识别端粒末端，从而提供一种机制，将端粒与哺乳动物中普遍存在的双链断裂修复途径隔离开来。我们在此表明，Ku 在体外与哺乳动物端粒 DNA 末端结合，并且 G 四联体构象无法阻止 Ku 以高亲和力与 DNA 结合。我们的结果表明，Ku 的 DNA 结合特征与其在哺乳动物细胞中与端粒 DNA 的直接相互作用以及其作为端粒末端因子的作用一致。
Ku is a heterodimeric protein with high binding affinity for ends, nicks, and gaps in double-stranded DNA. Both in mammalian cells and in budding yeast, Ku plays a role in nonhomologous end joining in the double strand break repair pathway. However, Ku has a more significant role in DNA repair in mammalian cells compared with yeast, in which a homology-dependent pathway is the predominant one. Recently Ku has been shown to be a likely component of the telomeric complex in yeast, suggesting the possibility of a similar role for Ku at mammalian telomeres, However, long single-stranded G-rich overhangs are continuously present at mammalian but not at yeast telomeres. These overhangs have the potential to fold in vitro into G-G base-paired conformations, such as G-quartets, that might prevent Ku from recognizing telomeric ends and thus offer a mechanism to sequester the telomere from the prevalent double strand break repair pathway in mammals. We show here that Ku binds to mammalian telomeric DNA ends in vitro and that G-quartet conformations are unable to prevent Ku from binding with high affinity to the DNA, Our results indicate that the DNA binding characteristics of Ku are consistent with its direct interaction with telomeric DNA in mammalian cells and its proposed role as a telomere end factor.