Brca1-Mediated Suppression Of Retrotransposon Activity - Resubmission - 1

项目摘要 LINE-1/L1反转录转座子是人类中唯一具有活性的自主非同源反转录转座子 基因组在人类基因组中，超过100个L1拷贝仍然能够移动，在细胞防御的环境中， 抑制反转录转座子的机制被"破坏"。越来越多的证据表明， L1蛋白表达和L1活性在正常过程中，如衰老，以及在疾病背景下， 癌症的发生和发展。基因组不稳定性是许多癌症的一个关键特征， 认为不仅是肿瘤发展的结果，而且是建立和 癌症的进展。我们最近的研究表明，LINE-1过表达和BRCA1基因的结合， 敲除导致一种新形式的基因组不稳定性，我们称之为染色体破碎。1号线，其 核酸内切酶和逆转录酶活性及其在基因组内"跳跃"的能力， 数量，在多个水平上参与染色质不稳定性。 全基因组筛选旨在确定抑制或支持L1运动（反转录转座）的因素 建立了肿瘤抑制基因BRCA1和同源重组（HR）修复与范可尼贫血 作为L1反转录转座的有效抑制剂。BRCA1（BReast CAncer 1）基因是一个公认的 肿瘤抑制基因的突变或缺失是许多乳腺癌、卵巢癌和其他人类肿瘤的原因。 癌的BRCA1蛋白是基于HR的DNA修复途径（高保真修复过程）中的关键参与者 在DNA复制期间由细胞实施以无缝地校正和修复可能有害的损伤。 BRCA1作为基因组完整性的守门人发挥作用，这一活动与癌症广泛相关。 BRCA1还涉及其他分子机制，如染色质重塑，转录 控制和翻译调节。 在这里，我们建议探索介导BRCA1抑制L1活性的分子机制。遗传的， 显微镜和生物化学方法将被实施，以剖析BRCA1之间的功能相互作用， 和L1反转录转位。BRCA1介导的L1抑制的基本机制的确定并不 它不仅能澄清L1语言生命周期中人们所知甚少的方面，而且也是解释L1语言的 在许多以BRCA1缺失为特征的癌症中起作用。

Project summary LINE-1/L1 retrotransposon is the only autonomous non-homologous retrotransposon active in the human genome. In the human genome, >100 copies of L1 are still able to move, in settings in which cellular defense mechanisms that repress retrotransposons are “breached”. Increasing evidence underscores the potential role of L1 protein expression and L1 activity in normal processes such as aging as well as in disease contexts like cancer initiation and progression. Genome instability is a key feature of many cancers and is increasingly considered not only a consequence of tumor development but a founding event for establishment and progression of cancer. Our recent work reveals that the combination of LINE-1 overexpression and BRCA1 knockdown leads to a novel form of genome instability we refer to as chromosome shattering. LINE-1, with its endonuclease and reverse transcriptase activity and its ability to “jump” within the genome increasing its copy number, is involved in chromatin instability at multiple levels. A whole genome screen aimed to identify factors that repress or support L1 movement (retrotransposition) established the tumor suppressor BRCA1 and the homologous recombination (HR) repair and Fanconi anemia pathways as potent inhibitors of L1 retrotransposition. The BRCA1 (BReast CAncer 1) gene is a well-established tumor suppressor the mutation or depletion of which is the cause of many breast, ovarian and other human cancers. The BRCA1 protein is a key player in the HR-based DNA repair pathway, a high fidelity repair process implemented by the cell during DNA replication to seamlessly correct and repair possibly deleterious damages. BRCA1 functions as a gatekeeper of genome integrity, an activity that has been extensively linked to cancer. BRCA1 has also been implicated in other molecular mechanisms such as chromatin remodeling, transcriptional control and translation regulation. Here we propose to explore the molecular mechanisms mediating BRCA1 suppression of L1 activity. Genetic, microscopy and biochemical approaches will be implemented to dissect functional interactions between BRCA1 and L1 retrotransposition. The identification of the basic mechanisms of BRCA1-mediated L1 suppression not only promises to clarify poorly understood facets of the L1 life-cycle but is also essential step to interpret L1’s role in the many cancers characterized by BRCA1 depletion.