Model Genetic Systems to Study DNA Repair

使用一种名为RNA干扰的方法，我们专门耗尽了人类细胞的FANCJ DNA解旋酶，并表征了细胞对稳定G-四链DNA结构的小分子化合物的敏感性。这项工作使我们能够阐明FANCJ解旋酶在维持染色体稳定性方面的一个新功能。由于携带FANCJ解旋酶基因纯合突变的个体患有一种名为Fanconi贫血的遗传性疾病，其特征是基因组不稳定和癌症，我们相信我们的结果为FANCJ的细胞通路提供了新的见解，这些途径有助于对抗由于体内出现的G-四链等可变DNA结构造成的复制应激。 我们已经使用了同基因对的突变和校正的鸡DT40细胞以及人类细胞进行遗传互补研究。突变的细胞系被用于患者来源的解旋酶失活突变的结构-功能研究。这项工作使我们能够确定临床相关突变和人类遗传病之间的基因-表型关系。这项工作的另一个方面是利用基因定义的癌症、正常细胞系和小分子来探索沃纳综合征解旋酶的分子和细胞功能。这些努力使我们能够确定抑制WRN解旋酶活性会在体内抑制细胞增殖及其DNA修复功能。基础科学方面的这些努力有助于推动这样一种观点，即DNA修复蛋白可能是抗癌治疗的靶点，以增加肿瘤对破坏DNA的化疗药物或辐射的敏感性。 我们还使用酵母作为模型遗传系统来研究Werner综合征解旋酶在DNA复制和修复中的作用。这项工作使我们能够表征WRN在一个定义的遗传DNA修复途径中的催化要求，该途径的运作是为细胞提供对施加复制应激的烷化剂的抵抗。 最后，我们利用小鼠作为模型遗传系统来表征在人类中发现的解旋酶同源基因(RECQ1)的作用，其生物学意义尚未被很好地理解。对RECQ1基因敲除小鼠胚胎成纤维细胞的鉴定表明，RECQ1解旋酶在维持基因组稳定性方面具有独特而重要的作用。

Using an approach known as RNA interference, we have specifically depleted human cells of the FANCJ DNA helicase and characterized the sensitivity of the cells to a small molecule compound that stabilizes G-quadruplex DNA structures. This work enabled us to elucidate a novel function of the FANCJ helicase in the manintenace of chromosomal stability. Since individuals carrying homozygous mutations in the FANCJ helicase gene have a genetic disorder known as Fanconi Anemia characterized by genomic instability and cancer, we believe our results shed new insights to the cellular pathways of FANCJ that serve to counter replciational stress due to alterante DNA structures such as G-quadruplexes that arise in vivo. We have used isogenic pairs of mutant and corrected chicken DT40 cells as well as human cells for genetic complementation studies. The mutant cell lines were used for structure-function studies of patient derived helicase-inactivating mutations. This work enabled us to define genotype-phenotype relationships between clinically relevant mutations and human genetic diseases. Another aspect of this work was to used genetically defined cancer and normal cell lines and small molecules to probed the molecualr and cellular functions of the Werner syndrome helicase. These efforts enabled us to determine that inhibition of WRN helicase activity inhibits cell proliferation and its DNA repair function in vivo. These efforts in the basic sciences help to advance the idea that DNA repair proteins may be targeted in anti-cancer therapy to increase the sensitivity of tumors to DNA damaging chemotherapy drugs or radiation. We have also employed yeast as a model genetic system to study the role of the Werner syndrome helicase in DNA replciation and repair. This work has enabled us to characterize the catalytic requirements of WRN in a defined genetic DNA repair pathway that operates to provide cellular resistance to alkylating agents which impose replicational stress. Lastly, we have utilized mouse as a model genetic system to characterize the role of a helicase ortholog (RECQ1) found in humans whose biological significance is not well understood. Characterization of th eprimary mouse embryonic fibroblasts from RECQ1 knockout mice has revealed that the RECQ1 helicase has unique and important roles in genomic stability maintenance.