Lodovichi Samuele, Vitello Martina, Cervelli Tiziana, Galli Alvaro
a Yeast Genetics and Genomics, Institute of Clinical Physiology , CNR, Pisa , Italy.
Cell Cycle. 2016 Oct 17;15(20):2723-31. doi: 10.1080/15384101.2016.1215389. Epub 2016 Aug 2.
BRCA1 tumor suppressor gene is found mutated in familial breast and ovarian cancer. Most cancer related mutations were found located at the RING (Really Interesting New Gene) and at the BRCT (BRca1 C-Terminal) domain. However, 20 y after its identification, the biological role of BRCA1 and which domains are more relevant for tumor suppression are still being elucidated. We previously reported that expression of BRCA1 cancer related variants in the RING and BRCT domain increases spontaneous homologous recombination in yeast indicating that BRCA1 may interact with yeast DNA repair/recombination. To finally demonstrate whether BRCA1 interacts with yeast DNA repair, we exposed yeast cells expressing BRCA1wt, the cancer-related variants C-61G and M1775R to different doses of the alkylating agent methyl methane-sulfonate (MMS) and then evaluated the effect on survival and homologous recombination. Cells expressing BRCA1 cancer variants were more sensitive to MMS and less inducible to recombination as compared to cell expressing BRCA1wt. Moreover, BRCA1-C61G and -M1775R did not change their nuclear localization form as compared to the BRCA1wt or the neutral variant R1751Q indicating a difference in the DNA damage processing. We propose a model where BRCA1 cancer variants interact with the DNA double strand break repair pathways producing DNA recombination intermediates, that maybe less repairable and decrease MMS-induced recombination and survival. Again, this study strengthens the use of yeast as model system to characterize the mechanisms leading to cancer in humans carrying the BRCA1 missense variant.
BRCA1肿瘤抑制基因在家族性乳腺癌和卵巢癌中被发现发生突变。大多数与癌症相关的突变位于RING（真有趣新基因）和BRCT（BRca1 C末端）结构域。然而，在其被鉴定20年后，BRCA1的生物学作用以及哪些结构域对肿瘤抑制更相关仍在阐明之中。我们先前报道，RING和BRCT结构域中与BRCA1癌症相关的变体的表达增加了酵母中的自发同源重组，这表明BRCA1可能与酵母DNA修复/重组相互作用。为了最终证明BRCA1是否与酵母DNA修复相互作用，我们将表达野生型BRCA1、癌症相关变体C-61G和M1775R的酵母细胞暴露于不同剂量的烷基化剂甲磺酸甲酯（MMS），然后评估对存活和同源重组的影响。与表达野生型BRCA1的细胞相比，表达BRCA1癌症变体的细胞对MMS更敏感，对重组的诱导性更低。此外，与野生型BRCA1或中性变体R1751Q相比，BRCA1-C61G和-M1775R的核定位形式没有改变，这表明在DNA损伤处理方面存在差异。我们提出了一个模型，其中BRCA1癌症变体与DNA双链断裂修复途径相互作用，产生可能较难修复的DNA重组中间体，并降低MMS诱导的重组和存活率。同样，这项研究加强了将酵母用作模型系统来表征携带BRCA1错义变体的人类癌症发生机制的应用。
