长链非编码RNA BGL3在DNA损伤修复应答中的功能和作用机制研究

Although BARD1/BRCA1 complex is a key player in homologous recombination repair (HR) and tumorigenesis, the regulation of BARD1/BRCA1 following DNA damage remains not fully understood. Especially, beyond protein whether RNA molecule is directly involved in BARD1/BRCA1 regulation is still largely unknown. We have found that a long noncoding RNA lncRNA-BGL3 participates in the HR pathway. Specifically, we found that lncRNA-BGL3 regulates BARD1/BRCA1 accumulation at DNA damage sites and BARD1 is the lncRNA-BGL3 binding protein. In response to DNA damage, lncRNA-BGL3 is recruited to DNA double strand break sites (DSBs) in a poly(ADP-ribose) dependent manner. Importantly, lncRNA-BGL3 expression is increased in breast cancer and correlates with poor survival. Depletion of lncRNA-BGL3 sensitizes breast cancer cells to radiation and PARP inhibitors, suggesting lncRNA-BGL3 might be a novel potential therapeutic target for breast cancer. Based on these preliminary findings, we hypothesize that lncRNA-BGL3 regulates BARD1/BRCA1 and DNA damage response, and that misregulation of lncRNA-BGL3 could affect response to radiation and chemotherapy. To further examine this hypothesis, we propose the following Specific Aims: 1. Investigate how lncRNA-BGL3 regulates BARD1/BRCA1 accumulation at DNA damage sites and affects DNA damage response. 2. Investigate how lncRNA-BGL3 is regulated by the DNA damage response pathway。Aim 3. Investigate the role of lncRNA-BGL3 in breast cancer initiaiton and response to radiochemotherapy. These studies will reveal a novel role of lncRNA-BGL3 in cellular response to genotoxic stress. Furthermore, the planned translational studies will define whether lncRNA-BGL3 is an important modulator of treatment response, which would provide key insight into why at least some breast cancer patients with dysregulation of lncRNA-BGL3 fare poorly with chemo-radiotherapy.

BRCA1是一个重要同源重组修复（HR）应答蛋白，与家族性乳腺癌发生密切相关。在临床上，PARP抑制剂特异性靶向治疗携带BRCA1突变的乳腺癌。BARD1能和BRCA1形成二聚体，调控DNA双链断裂末端剪切和同源重组，但其调控机制仍不十分清楚。我们前期发现长链非编码RNA BGL3直接调控HR和基因组稳定性，BARD1是一个lncRNA结合蛋白。DNA损伤发生后，LncRNA-BGL3被招募到DNA损伤修复位点，结合BARD1，调控BARD1/BRCA1在DNA损伤位点处的聚集和DNA双链断裂末端剪切。本研究中，我们拟进一步深入研究lncRNA-BGL3在HR中的功能和作用分子机制，用临床样本和裸鼠模型研究lncRNA-BGL3与乳腺癌发生和PARP抑制剂应答的关系。本课题的开展将为LncRNA在基因组稳定性中的功能提供新的线索，为基于LncRNA-BGL3的乳腺癌的防治提供新的理论基础。

长非编码RNAs（lncRNAs）是一种新兴的基因组稳定性和人类疾病的调节器。然而，核lnRNAs直接促进DNA损伤反应的分子机制在很大程度上仍然未知。使用RNA反义纯化与定量质谱（RAPqMS）相结合的分析方法，我们发现lncRNA BGL3与PARP1和BARD1的结合在同源重组中表现出意想不到的作用。从机制上来讲，BGL3在早期就被PARP1招募到DNA双链断裂（DSB）处，这依赖于它与PARP1的DNA相互结合域。BGL3还能与BARD1的C端BRCT结构域和一个内部区域（127-424个氨基酸）结合，调控BRCA1/BARD1复合物与其结合伙伴如HP1c和RAD51的相互作用，导致BRCA1/BARD1保留在DSBs，去除BGL3的细胞显示出基因组不稳定并且对DNA损伤试剂敏感。总的来说，我们的发现强调了RNA作为DNA损伤反应途径中的中介分子的生物化学多样性，它影响了BRCA1/BARD1在DSBs的积累。