Screening and analyses of novel BRCA1/2-associated proteins

BRCA2种系突变是遗传性乳腺癌和卵巢癌的主要原因。除了在DNA损伤修复中的作用外，BRCA2可能还在中心体扩增中发挥作用，因为BRCA2定位于中心体和细胞核，并且中心体中BRCA2的功能障碍会导致细胞分裂异常。通过质谱分析，我们鉴定出核磷蛋白（NPM）和Rho-associated coil -coil containing protein kinase 2 （ROCK2）是新的brca2相关蛋白。由于已知ROCK2在中心体上与NPM结合，这3种蛋白可能形成复合物。BRCA2中的npm结合区位于639- 1000个氨基酸内。该BRCA2区域的外源表达导致中心体异常扩增和多核细胞的高频率。我们的研究结果表明，由BRCA2、NPM和ROCK2组成的复合体维持着中心体的数量完整性和精确的细胞分裂，这种调节的功能障碍可能参与了乳腺癌的肿瘤发生。

BRCA2 germline mutations account for the majority of heredity breast and ovarian cancer. Besides its role in DNA damage repair, it was hypothesized that BRCA2 might have a role in centrosomal amplification, since BRCA2 localizes to centrosomes as well as nuclei and the dysfunction of BRCA2 in a centrosome causes abnormalities in cell division. We identified nucleophosmin (NPM) and Rho-associated coiled-coil containing protein kinase 2 (ROCK2) as novel BRCA2-associated proteins by mass spectrometry. Because it is known that ROCK2 binds to NPM at centrosomes, these 3 proteins may form a complex. NPM-binding region in BRCA2 was determined to be within amino acids 639-1,000. Exogenous expression of this BRCA2 region resulted in aberrant centrosome amplification and a high frequency of multinucleated cells. Our results suggested that a complex consisting of BRCA2, NPM, and ROCK2 maintains the numerical integrity of centrosomes and accurate cell division and that dysfunction of this regulation might be involved in the tumorigenesis of breast cancer.