BRCA2 BRC missense variants disrupt RAD51-dependent DNA repair.
BRCA2 BRC missense variants disrupt RAD51-dependent DNA repair.
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DOI：
10.7554/elife.79183
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发表时间：
2022-09-13
期刊：
影响因子：
7.7
通讯作者：
Jensen RB
中科院分区：
文献类型：
--
作者：
Jimenez-Sainz J;Mathew J;Moore G;Lahiri S;Garbarino J;Eder JP;Rothenberg E;Jensen RB
BRCA 2肿瘤抑制基因的致病性突变易患乳腺癌、卵巢癌、胰腺癌、前列腺癌和其他癌症。BRCA 2通过DNA双链断裂（DSB）的同源定向修复（HDR）和复制叉保护来维持基因组稳定性。导致BRCA 2蛋白截短的无义突变或移码突变通常被认为是致病性的;然而，导致单个氨基酸取代的错义突变在功能上可能具有挑战性。BRCA 2中的大多数错义突变已被归类为具有未知功能后果的不确定意义变体（VUS）。在这项研究中，我们确定了三个BRCA 2 VUS位于BRC重复区域，以确定它们对典型HDR和分叉保护功能的影响。我们提供的证据表明，S1221 P和T1980 I，映射到BRC 2和BRC 7重复序列中的保守残基，损害细胞对化疗和电离辐射的反应，并显示叉保护缺陷。我们进一步证明了S1221 P和T1980 I在生物化学上破坏了RAD 51的结合，并降低了BRCA 2稳定RAD 51-ssDNA复合物的能力。第三个变体T1346 I位于BRC 2和BRC 3重复序列之间的间隔区，具有完全功能。我们得出的结论是，T1346 I是良性等位基因，而S1221 P和T1980 I是亚纯型的，破坏了BRCA 2完全接合和稳定RAD 51核蛋白丝的能力。我们的结果强调了将BRCA 2 VUS正确分类为致病性变体的重要性，可以影响未来的癌症风险并指导癌症治疗期间的治疗选择。
Pathogenic mutations in the BRCA2 tumor suppressor gene predispose to breast, ovarian, pancreatic, prostate, and other cancers. BRCA2 maintains genome stability through homology-directed repair (HDR) of DNA double-strand breaks (DSBs) and replication fork protection. Nonsense or frameshift mutations leading to truncation of the BRCA2 protein are typically considered pathogenic; however, missense mutations resulting in single amino acid substitutions can be challenging to functionally interpret. The majority of missense mutations in BRCA2 have been classified as Variants of Uncertain Significance (VUS) with unknown functional consequences. In this study, we identified three BRCA2 VUS located within the BRC repeat region to determine their impact on canonical HDR and fork protection functions. We provide evidence that S1221P and T1980I, which map to conserved residues in the BRC2 and BRC7 repeats, compromise the cellular response to chemotherapeutics and ionizing radiation, and display deficits in fork protection. We further demonstrate biochemically that S1221P and T1980I disrupt RAD51 binding and diminish the ability of BRCA2 to stabilize RAD51-ssDNA complexes. The third variant, T1346I, located within the spacer region between BRC2 and BRC3 repeats, is fully functional. We conclude that T1346I is a benign allele, whereas S1221P and T1980I are hypomorphic disrupting the ability of BRCA2 to fully engage and stabilize RAD51 nucleoprotein filaments. Our results underscore the importance of correctly classifying BRCA2 VUS as pathogenic variants can impact both future cancer risk and guide therapy selection during cancer treatment.