The role of nonhomologous end-joining components in telomere metabolism in Kluyveromyces lactis
The role of nonhomologous end-joining components in telomere metabolism in Kluyveromyces lactis
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DOI：
10.1534/genetics.106.067447
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发表时间：
2007-03-01
期刊：
影响因子：
3.3
通讯作者：
Astrom, Stefan U.
中科院分区：
文献类型：
--
作者：
Carter, Sidney D.;Iyer, Shilpa;Astrom, Stefan U.
端粒和非同源末端连接（NHEJ）之间的关系是矛盾的，因为NHEJ蛋白是端粒帽的一部分，用于区分端粒和DNA双链断裂。我们通过研究NHEJ蛋白在乳酸克鲁维酵母端粒代谢中的作用，探索了这些相互矛盾的功能。TER 1基因的ter 1 -4LBsr等位基因导致引入序列改变的端粒重复序列和随后的端粒-端粒融合（T-TF）。在此背景下，Lig 4和Ku 80是T-TF形成所必需的。Nej 1，NHEJ在内部位置必不可少的，不是。因此，T-TF的形成是由一个不寻常的NHEJ机制介导的。Rad 50和Mre 11菌株表现出稳定的短端粒，表明Rad 50和Mre 11是端粒酶募集所必需的。将ter 1 -4LBsr等位基因引入这些菌株中未能导致端粒延长，如通常观察到的ter 1 -4LBsr等位基因。因此，Rad 50和Mre 11在T-TF形成中的作用尚不清楚。此外，rad 50和mre 11突变体具有高度增加的亚端粒重组率，而ku 80和lig 4突变体显示中度增加。Ku 80突变株还含有延伸的单链3'端粒突出端。我们得出结论，NHEJ蛋白在端粒中具有多种作用，介导突变端粒的融合并确保正常端粒的末端保护。
The relationship between telomeres and nonhomologous end-joining (NHEJ) is paradoxical, as NHEJ proteins are part of the telomere cap, which serves to differentiate telomeres from DNA double-strand breaks. We explored these contradictory functions for NHEJ proteins by investigating their role in Kluyveromyces lactis telomere metabolism. The ter1-4LBsr allele of the TER1 gene resulted in the introduction of sequence altered telomeric repeats and subsequent telomere-telomere fusions (T-TFs). In this background, Lig4 and Ku80 were necessary for T-TFs to form. Nej1, essential for NHEJ at internal positions, was not. Hence, T-TF formation was mediated by an unusual NHEJ mechanism. Rad50 and mre11 strains exhibited stable short telomeres, suggesting that Rad50 and Mre11 were required for telomerase recruitment. Introduction of the ter1-4LBsr allele into these strains failed to result in telomere elongation as normally observed with the ter1-4LBsr allele. Thus, the role of Rad50 and Mre11 in the formation of T-TFs was unclear. Furthermore, rad50 and mre11 mutants had highly increased subtelomeric recombination rates, while ku80 and lig4 mutants displayed moderate increases. Ku80 mutant strains also contained extended single-stranded 3' telomeric overhangs. We concluded that NHEJ proteins have multiple roles at telomeres, mediating fusions of mutant telomeres and ensuring end protection of normal telomeres.