Complex Breakpoints and Template Switching Associated with Non-canonical Termination of Homologous Recombination in Mammalian Cells.
Complex Breakpoints and Template Switching Associated with Non-canonical Termination of Homologous Recombination in Mammalian Cells.
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DOI：
10.1371/journal.pgen.1006410
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发表时间：
2016-11
期刊：
影响因子：
4.5
通讯作者：
Scully R
中科院分区：
文献类型：
--
作者：
Hartlerode AJ;Willis NA;Rajendran A;Manis JP;Scully R
哺乳动物细胞中的一部分同源重组（HR）事件通过“长束”基因转换解决，反映了终止前从供体姐妹染色单体复制的几种酶。缺乏主要遗传性乳腺癌/卵巢癌易感基因BRCA 1或BRCA 2的细胞，或某些其他HR缺陷细胞，显示出有利于长链基因转换的偏倚，表明这种异常的HR结果可能与基因组不稳定性有关。如果基因转换的终止发生在与断裂的第二末端缺乏同源性的区域，则通过退火的HR终止的正常机制（即，同源配对）是不可用的，并且终止必须通过尚未明确定义的非规范机制发生。在这里，我们使用以前描述的HR报告分析机制的非规范终止的长道基因转换在哺乳动物细胞。我们发现，非典型的HR终止可以发生在经典的非同源末端连接基因XRCC 4的情况下。我们观察到强制性使用微同源（MH）介导的末端连接和/或核苷酸添加过程中重新加入与第二端的休息。值得注意的是，非典型HR终止与复杂断点相关。我们确定同源介导的模板转换的作用，并可能，MH介导的模板转换/微同源介导的中断诱导复制，在非经典HR终止位点的复杂断点的形成。这项工作确定了非典型的HR终止作为基因组不稳定性和癌症中复杂断点形成的潜在贡献者。复杂的断裂点是癌症基因组重排的公认特征，但导致其形成的机制尚不明确。虽然同源重组（HR）被认为是一种潜在的无错误途径，但缺乏关键HR基因（如主要遗传性乳腺癌/卵巢癌易感基因BRCA 1或BRCA 2）的细胞经常参与易错同源重组机制，其中HR终止不会及时发生。我们在这里表明，在哺乳动物细胞中的HR异常终止涉及使用易错的替代末端连接机制，并可能导致通过模板转换机制形成复杂的断点。这表明同源重组的缺陷性终止是在癌细胞中观察到的一些复杂断点的基础。
A proportion of homologous recombination (HR) events in mammalian cells resolve by “long tract” gene conversion, reflecting copying of several kilobases from the donor sister chromatid prior to termination. Cells lacking the major hereditary breast/ovarian cancer predisposition genes, BRCA1 or BRCA2, or certain other HR-defective cells, reveal a bias in favor of long tract gene conversion, suggesting that this aberrant HR outcome might be connected with genomic instability. If termination of gene conversion occurs in regions lacking homology with the second end of the break, the normal mechanism of HR termination by annealing (i.e., homologous pairing) is not available and termination must occur by as yet poorly defined non-canonical mechanisms. Here we use a previously described HR reporter to analyze mechanisms of non-canonical termination of long tract gene conversion in mammalian cells. We find that non-canonical HR termination can occur in the absence of the classical non-homologous end joining gene XRCC4. We observe obligatory use of microhomology (MH)-mediated end joining and/or nucleotide addition during rejoining with the second end of the break. Notably, non-canonical HR termination is associated with complex breakpoints. We identify roles for homology-mediated template switching and, potentially, MH-mediated template switching/microhomology-mediated break-induced replication, in the formation of complex breakpoints at sites of non-canonical HR termination. This work identifies non-canonical HR termination as a potential contributor to genomic instability and to the formation of complex breakpoints in cancer. Complex breakpoints are a recognized feature of cancer genome rearrangements, but the mechanisms that lead to their formation are undefined. Although homologous recombination (HR) is considered a potentially error-free pathway, cells lacking critical HR genes, such as the major hereditary breast/ovarian cancer predisposition genes, BRCA1 or BRCA2, frequently engage error-prone homologous recombination mechanisms in which HR termination does not occur in a timely fashion. We show here that aberrant termination of HR in mammalian cells involves the use of error-prone alternative end joining mechanisms and can lead to the formation of complex breakpoints by means of template switching mechanisms. This suggests that defective termination of homologous recombination underlies some of the complex breakpoints observed in cancer cells.
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影响因子：
64.5
作者：
Alt FW;Zhang Y;Meng FL;Guo C;Schwer B
通讯作者：
Schwer B
影响因子：
14.9
作者：
Yu AM;McVey M
通讯作者：
McVey M
影响因子：
64.8
作者：
Cox, MM;Goodman, MF;Marians, KJ
通讯作者：
Marians, KJ
DOI：
10.1126/science.aaa8391
发表时间：
2015-08-14
期刊：
Science (New York, N.Y.)
影响因子：
--
作者：
Mayle R;Campbell IM;Beck CR;Yu Y;Wilson M;Shaw CA;Bjergbaek L;Lupski JR;Ira G
通讯作者：
Ira G
影响因子：
64.5
作者：
Lambert, S;Watson, A;Carr, AM
通讯作者：
Carr, AM