NUCKS, a novel double-strand break repair gene, implicated in cancer biology

描述（由申请方提供）：DNA双链断裂（DSB）是一种高毒性DNA损伤，可在DNA复制期间自发发生，但也可通过暴露于电离辐射（IR）或化学诱变剂引入。DSB可导致细胞死亡、突变和癌症，并且DSB修复（DSBR）缺陷是许多人类疾病的基础，包括与癌症易感性、辐射敏感性、免疫功能障碍、神经变性和过早衰老相关的病症。核内普遍存在的酪蛋白和细胞周期蛋白依赖性激酶底物（NUCKS）是一种分子量为27 kD的脊椎动物特异性DNA结合蛋白。NUCKS在快速生长的细胞中大量存在，并在多种人类癌症中过表达。特别令人感兴趣的是，NUCKS基因位于人类染色体1q32.1上，这是一个通常在乳腺癌中获得的区域。基于与同源重组修复（HRR）中的关键因子RAD 51相关蛋白1（RAD 51 AP 1）的序列同源性，我们已经测试并确定了NUCKS在DSBR中的作用。我们的研究结果表明，NUCKS敲低的人类细胞对IR和化学诱变剂过敏，NUCKS不仅调节HRR，而且调节G1期细胞对IR的细胞抗性。在使用杂合Trp 53小鼠的初步实验中，我们发现Nucks功能受损显著增加了对IR诱导的肿瘤的易感性，改变了肿瘤谱并促进了转移。我们现在打算进一步定义NUCKS如何使用生物化学和基于细胞的测定来调节DSBR能力（目的1和2）。此外，我们将进行系统研究，以进一步确定小鼠中Nucks破坏的表型后果（目的2）。我们的研究结果显示NUCKS在DSBR和防止辐射致癌中的作用，这是NUCKS生物学功能的第一个证据，NUCKS是一种25年前发现的蛋白质。考虑到DSBR和HRR在肿瘤抑制和去除IR和其他环境诱变剂诱导的DNA损伤中的重要性，我们的研究结果将与环境因素对健康的风险预测直接相关。此外，我们的研究也可能有助于改善癌症的诊断、预防和治疗。 公共卫生相关性：同源重组修复（HRR）是维持基因组稳定性和预防癌症不可或缺的，这种修复机制在BRCA 1/2相关的乳腺癌中受损。NUCKS（Nuclear Ubiquitous Casein and Cyclin-dependent Kinases Substrate）是参与HRR途径的重要蛋白质，并且是电离辐射和几种化疗剂引起的DNA损伤的修复所必需的。拟议的研究旨在进一步阐明NUCKS在HRR和癌症相关过程中的作用，并将为理解DNA修复在癌症避免中的作用做出重要贡献。

DESCRIPTION (provided by applicant): DNA double-strand breaks (DSBs) are highly toxic DNA lesions that can occur spontaneously during DNA replication, but also can be introduced by exposure to ionizing radiation (IR) or to chemical mutagens. DSBs can lead to cell death, mutations and cancer, and defects in DSB repair (DSBR) underlie many human diseases, including disorders associated with cancer predisposition, radiosensitivity, immune dysfunction, neurodegeneration and premature aging. Nuclear Ubiquitous Casein and Cyclin-dependent Kinases Substrate (NUCKS) is a 27 kD, DNA-binding and vertebrate-specific protein with unknown function. NUCKS is abundant in rapidly growing cells and overexpressed in a variety of human cancers. Of particular interest, the NUCKS gene is located on human chromosome 1q32.1, a region that is commonly gained in breast cancer. Based on sequence homology to RAD51 Associated Protein 1 (RAD51AP1), a critical factor in homologous recombination repair (HRR), we have tested and determined a role for NUCKS in DSBR. Our results show that human cells with NUCKS knockdown are hypersensitive to IR and to chemical mutagens, and that NUCKS regulates not only HRR, but also cellular resistance to IR in G1-phase cells. In preliminary experiments using mice with heterozygous Trp53, we find that impaired Nucks function significantly increases the susceptibility to IR-induced tumors, alters the tumor spectrum and promotes metastasis. We now intend to further define how NUCKS regulates DSBR capacity using biochemical and cell-based assays (Aims 1 & 2). In addition, we will carry out a systematic study to further determine the phenotypic consequences of Nucks disruption in mice (Aim 2). Our findings showing a role for NUCKS in DSBR and in preventing radiation carcinogenesis are the first evidence for a biological function of NUCKS, a protein that was discovered more than 25 years ago. Given the importance of DSBR and HRR in tumor suppression and in the removal of DNA lesions induced by IR and other environmental mutagens, the results from our investigation will have direct relevance to risk predictions for health from environmental factors. In addition, our studies may also contribute to the improved diagnosis, prevention and treatment of cancer. PUBLIC HEALTH RELEVANCE: Homologous recombination repair (HRR) is indispensable for maintaining genomic stability and preventing cancer, and this repair mechanism is impaired in BRCA1/2-related breast cancers. NUCKS (Nuclear Ubiquitous Casein and Cyclin-dependent Kinases Substrate) is an important protein involved in the HRR pathway, and is required for the repair of DNA damage caused by ionizing radiation and several chemotherapeutic agents. The proposed studies are designed to further elucidate the role of NUCKS in HRR and cancer-relevant processes, and will make an important contribution to understanding the role of DNA repair in cancer avoidance.