Functions of the BLM Helicase in Telomere Maintenance

BLM 解旋酶在端粒维护中的功能

基本信息

批准号：
7474314
负责人：
Joanna Louise Groden
金额：
$ 31.13万
依托单位：
OHIO STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2008
资助国家：
美国
起止时间：
2008-05-01 至 2013-02-28
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7474314
关键词：
Affect Age All Sites BLM gene Binding Proteins Bloom Syndrome Bloom syndrome protein Cancer Cell Growth Cell Cycle Cells Chromosome Breakage Chromosomes Complex DNA DNA Damage DNA Double Strand Break Data Double Strand Break Repair Gene Proteins Genes Genetic Recombination Genetically Engineered Mouse Genome Stability Genomics Goals Heat-Shock Proteins 90 Hereditary Disease Homologous Gene Human Human Genome Immunohistochemistry Immunologic Deficiency Syndromes Immunoprecipitation In Vitro Individual Inherited Laboratories Learning Localized Maintenance Male Infertility Malignant Neoplasms Mammalian Cell Mediating Mitosis Modification Mutate Nonhomologous DNA End Joining Normal Cell Nucleic Acids Phospho-Specific Antibodies Phosphorylation Site Photosensitivity Post-Translational Protein Processing Predisposition Process Proteins Public Health Regulation Role Syndrome TEP1 gene TERF1 gene Telomerase Telomere Maintenance Telomeric Repeat Binding Protein 1 Testing Therapeutic Thinking Topoisomerase WRN gene Work Yeasts helicase homologous recombination immortalized cell in vitro Assay in vivo intracellular protein transport mutant neoplastic novel oncology positional cloning protein expression protein localization location repaired telomere

项目摘要

DESCRIPTION (provided by applicant): Human BLM encodes a recQ-like DNA helicase that is important for the maintenance of genomic stability. When both copies of this gene are mutated, the resulting hereditary disease, known as Bloom's syndrome (BS), is characterized by sun-sensitivity, small stature, immunodeficiency, male infertility, and a tremendous predisposition to cancer of all sites and types. Cells from BS individuals are characterized by chromosome breakage and other chromosomal anomalies that are indicative of increased somatic recombination. Notably, telomeric associations (TAs) between homologous chromosomes are also present in non- immortalized and immortalized cells from BS individuals. Following the positional cloning of the BLM gene, our laboratory has investigated the functions of the BLM helicase in DNA double strand break repair processes such as non-homologous end joining, homologous recombination-mediated repair, and synthesis-dependent strand annealing. Our work has also suggested a role for BLM in recombination- mediated mechanisms of telomere elongation or ALT (alternative lengthening of telomeres), processes that maintain/elongate telomeres in the absence of telomerase. BLM preferentially associates with the telomere- specific binding proteins TRF1 and TRF2 in cells using ALT; its helicase activity can be modulated by these interactions. Our preliminary data identify and validate other proteins that uniquely interact with BLM and TRF2 in cells using ALT, demonstrate that these protein interactions modify enzymatic activity of BLM and its partner topoisomerase IIalpha, and show that modification of five putative phosphorylation sites can alter unwinding of DNA substrates. We hypothesize that BLM complex formation and modification occur dynamically during the specific nucleic acid transactions that are required to protect the telomere, to align chromosome sequences at homologous telomeres, to permit strand invasion and elongation, and/or ultimately to disentangle telomeres. These ideas will be investigated by analyses of BLM modification, localization and protein partnering during telomere elongation, and by modifying these interactions or modifications in vitro and in vivo using genetically engineered mice. The immediate goal of this application is to determine the mechanism by which BLM functions to maintain telomeres. This work has important implications for learning how cells maintain their genomic integrity, how they age or become immortal, and ultimately for developing better therapeutic strategies in oncology. PUBLIC HEALTH RELEVANCE: Inherited syndromes that predispose to cancer have provided us an opportunity to study the genes and proteins that are important for keeping normal cells from becoming neoplastic. The BLM helicase is one of these proteins, as it seems to be required to maintain stability of the human genome. Its role in the maintenance of chromosome ends is especially important, as it is these mechanisms that enable cells to gain the ability to grow indefinitely. The study of BLM therefore represents an opportunity for us to learn how we can control the growth of cancer cells in a therapeutic setting.

描述（由申请人提供）：人类 BLM 编码一种类似 recQ 的 DNA 解旋酶，该酶对于维持基因组稳定性非常重要。当该基因的两个拷贝都发生突变时，就会产生一种称为布卢姆综合症 (BS) 的遗传性疾病，其特征是对阳光敏感、身材矮小、免疫缺陷、男性不育以及极易患各种部位和类型的癌症。来自 BS 个体的细胞的特征是染色体断裂和其他染色体异常，这些异常表明体细胞重组增加。值得注意的是，同源染色体之间的端粒关联(TA)也存在于来自BS个体的非永生化和永生化细胞中。在BLM基因的定位克隆之后，我们实验室研究了BLM解旋酶在DNA双链断裂修复过程中的功能，例如非同源末端连接、同源重组介导的修复和合成依赖性链退火。我们的工作还表明 BLM 在重组介导的端粒延长或 ALT（端粒选择性延长）机制中发挥作用，这是在端粒酶缺失的情况下维持/延长端粒的过程。 BLM 使用 ALT 优先与细胞中的端粒特异性结合蛋白 TRF1 和 TRF2 结合；其解旋酶活性可以通过这些相互作用来调节。我们的初步数据使用 ALT 识别并验证了细胞中与 BLM 和 TRF2 独特相互作用的其他蛋白质，证明这些蛋白质相互作用改变了 BLM 及其伙伴拓扑异构酶 IIalpha 的酶活性，并表明五个假定的磷酸化位点的修饰可以改变 DNA 的解旋基材。我们假设 BLM 复合物的形成和修饰在保护端粒、在同源端粒处对齐染色体序列、允许链侵入和延伸和/或最终解开端粒所需的特定核酸交易过程中动态发生。这些想法将通过分析端粒延长过程中的 BLM 修饰、定位和蛋白质配对，并使用基因工程小鼠在体外和体内修改这些相互作用或修饰来研究。该应用的直接目标是确定 BLM 维持端粒的机制。这项工作对于了解细胞如何维持其基因组完整性、它们如何衰老或永生以及最终开发更好的肿瘤学治疗策略具有重要意义。公共健康相关性：易患癌症的遗传综合征为我们提供了研究基因和蛋白质的机会，这些基因和蛋白质对于防止正常细胞变成肿瘤很重要。 BLM 解旋酶就是其中一种蛋白质，因为它似乎是维持人类基因组稳定性所必需的。它在维持染色体末端方面的作用尤其重要，因为正是这些机制使细胞获得无限生长的能力。因此，BLM 的研究为我们提供了一个了解如何在治疗环境中控制癌细胞生长的机会。