DNA Repair In Cancer And Senescence

工作概述：Werner’s syndrome （WS）是一种纯合隐性疾病，其特征是早期出现许多正常衰老的特征，如皮肤起皱、头发变白、白内障、糖尿病和骨质疏松症。WS的症状在青春期左右开始出现，大多数患者在50岁之前死亡。由于WS中衰老的加速，对这种疾病的研究有望揭示正常衰老中发生的退行性过程。与年龄匹配的正常细胞相比，来自WS患者的细胞生长更慢，衰老的时间更早，数量增加了一倍，可能是因为这些细胞似乎以更快的速度失去了染色体的端粒末端。一般来说，WS细胞具有高度的基因组不稳定性，DNA缺失、插入和重排的数量增加。这些影响可能是DNA修复、复制和/或重组缺陷的潜在结果，尽管实际的生化缺陷尚不清楚。在WS中有缺陷的基因WRN基因已经被鉴定和表征。我们已经制备了纯化的WRN蛋白，用于许多基础和复杂的生化分析。我们正在寻求几种途径来识别和表征WS细胞中的生化缺陷。WRN蛋白具有解旋酶活性，可以解开大小DNA双链结构。它还将解开不寻常的DNA结构，如三螺旋和DNA分叉。我们将Werner解旋酶的活性与另一种解旋酶BLM的活性进行比较，BLM在Bloom综合征中发生突变。WRNp具有另一种酶活性，即3-5'外切酶功能。我们正在寻找WRN参与的途径，并发现了许多新的功能和物理蛋白与Werner蛋白的相互作用。我们的数据强烈表明，WRN参与了两种主要的DNA修复途径：碱基切除修复和重组。这一结论得到了蛋白质功能相互作用的生化研究和越来越多的细胞生物学数据的支持。此外，我们的观察和其他工作的结果表明，WRN的主要功能是在端粒端。WRN与许多关键的端粒蛋白如TRF1、2和POT1相互作用。这些功能性蛋白相互作用的观察结果被细胞生物学观察证实，表明WRN蛋白在端粒端参与DNA修复过程和维护。

Summary of work: Werner's syndrome (WS) is a homozygous recessive disease characterized by early onset of many characteristics of normal aging, such as wrinkling of the skin, graying of the hair, cataracts, diabetes, and osteoporosis. The symptoms of WS begin to appear around the age of puberty, and most patients die before age 50. Because of the acceleration of aging in WS, the study of this disease will hopefully shed light on the degenerative processes that occur in normal aging. Cells from WS patients grow more slowly and senescence at an earlier population doubling than age-matched normal cells, possibly because these cells appear to lose the telomeric ends of their chromosomes at an accelerated rate. In general, WS cells have a high level of genomic instability, with increased amounts of DNA deletions, insertions, and rearrangements. These effects could potentially be the result of defects in DNA repair, replication, and/or recombination, although the actual biochemical defect remains unknown. The gene that is defective in WS, the WRN gene, has been identified and characterized. We have made purified WRN protein for use in a number of basic and complex biochemical assays. We are pursuing several avenues to identify and characterize the biochemical defect in WS cells. WRN protein has helicase activity and will unwind small and large DNA duplex constructs. It will also unwind unusual DNA structures such as triple helices and DNA forks. We are comparing the Werner helicase activity to that of another helicase, BLM, which is mutated in Bloom syndrome. WRNp has another enzymatic activity, a 3-5' exonuclease function. We are searching for pathways in which WRN participates and have discovered a number of new functional and physical protein interactions with Werner protein. Our data strongly suggest that WRN is involved in two of the major DNA repair pathways: base excision repair and recombination. This conclusion is supported by biochemical studies of protein functional interaction and increasingly also by cell biological data. Further, our observations and results from other work suggest that a major function of WRN is at the telomere end. WRN interacts with a number of key telomeric proteins such as TRF1 and 2 and POT1. These observations of functional protein interactions corroborated by cell biological observations suggest that WRN protein is involved in DNA repair processes and maintenance at the telomere end.