Determining how global genome nucleotide excision repair promotes efficient removal of DNA damage from chromatin

我们每个细胞中都包含着生命所必需的编码信息。这些信息被储存在一个叫做细胞核的细胞隔间里，细胞核里有一个大分子，它具有一种特殊的结构，叫做脱氧核糖核酸——DNA。DNA中的信息被分成称为染色体的单位，染色体又被进一步细分为基因。DNA被包装成染色质是为了压缩细胞核中的遗传物质，生物体的所有遗传物质的总和被称为其基因组。可以预见，生命的编码信息会非常稳定，不会改变，因为编码中的错误可能会导致严重的后果。另一方面，生物能够适应环境的变化，是由于个体遗传物质的改变导致种群内的遗传变异。这个过程被称为进化。在人类种群中，许多遗传变异是有性生殖过程中基因“重组”的结果。然而，DNA也会被细胞内的正常过程以及环境的物理或化学损伤所改变，包括来自阳光的紫外线辐射。我们每个细胞中的DNA都在不断地被这些物质破坏。如果不加以控制，这将迅速侵蚀遗传信息，因为细胞分裂时复制受损的DNA会永久地改变遗传密码——这一过程被称为突变。随着时间的推移，各种不同的DNA修复途径已经进化出来，以防止这种情况的发生。总的来说，这些都是基因组稳定的基础。遗传了控制这些DNA修复途径的基因缺陷的人更有可能患上某些癌症和其他疾病。我们的研究旨在了解这些过程中的一个，核苷酸切除修复（NER）是如何运作的。调节这一过程的基因有缺陷的人患皮肤癌和其他癌症的几率很高。分子研究揭示了参与这一过程的不同基因的缺陷如何导致许多临床不同的疾病。我们的大部分知识都来自于对各种不同生物体内NER的研究。我们研究面包酵母中的NER。令人惊讶的是，酵母的机制与人类细胞非常相似，强调了这一过程的基本意义。本提案中描述的工作旨在帮助我们了解NER过程如何在基因组中组织，以及紫外线诱导的DNA损伤后如何从染色质上去除病变。染色质中DNA损伤的传感器在细胞中如何调节DNA修复中起着重要作用。DNA修复的研究已经进入了一个新的发现阶段，揭示了各种DNA修复机制是如何被控制以响应DNA损伤的，以及这些途径是如何相互整合的。除了提高我们对人类疾病综合征的分子基础的理解外，这些途径之间新的合成遗传相互作用正在为新的和改进的癌症治疗确定新的靶点。目前，我们对NER通路在染色质中如何运作以及这一过程如何被调节的了解落后于我们对其他修复通路的了解。本提案中开展的工作将大大提高我们在这一领域的知识，为进一步的人类研究提供重要的见解。

Contained within each of our cells is the coded information necessary for life. The information is stored in a compartment of the cell called the nucleus which contains a large molecule with a remarkable structure called deoxyribonucleic acid - DNA. The information within the DNA is divided into units called chromosomes which are further subdivided into genes. DNA is packaged into chromatin in order to compact the genetic material in the nucleus and the sum of all the genetic material of an organism is referred to as its genome. It might be anticipated that life's coded information would be extremely stable and resistant to change, since errors in the code could have serious consequences. On the other hand, organisms are able to adapt to changes in their environment by virtue of the genetic variation within the population caused by alterations in the genetic material of individuals. This process is known as evolution. In the human population a lot of genetic variation is the result of 'reshuffling' of the genes during sexual reproduction. However, DNA can also be altered by normal processes operating within the cell, as well as physical or chemical damage from the environment, including ultraviolet radiation from sunlight. The DNA in each of our cells is continuously damaged by such agents. If left unchecked this would quickly erode the genetic information, since copying damaged DNA when cells divide can permanently alter the genetic code - a process called mutation. Over time, a variety of different DNA repair pathways have evolved which serve to prevent this from occuring. Collectively these are fundamental to the stability of the genome. People who inherit defects in the genes controlling these DNA repair pathways are more likely to suffer from certain cancers and other diseases. Our research aims to understand how one of these processes, nucleotide excision repair [NER] operates. People with defects in genes regulating this process suffer highly elevated levels of skin and other cancers. Molecular studies have revealed how defects in different genes involved in the process can result in a number of clinically distinct diseases. Much of our knowledge has come from the study of NER in a variety of different organisms. We study NER in bakers' yeast. Amazingly, the mechanism in yeast is remarkably similar to that in human cells, underlining the fundamental significance of this process. The work described in this proposal aims to help us understand how the NER process is organised in the genome and how lesions are removed from chromatin following UV induced DNA damage. It is emerging that the sensors of DNA damage in chromatin are playing an important role in how DNA repair is regulated in the cell. Research into DNA repair has entered a new phase of discovery, revealing how the various DNA repair mechanisms are controlled in response to DNA damage and how the pathways are integrated with one another. In addition to improving our understanding of the molecular basis of human disease syndromes, novel synthetic genetic interactions between the pathways are identifying new targets for novel and improved cancer treatments. At present our knowledge of how the NER pathway operates in chromatin and how this process is regulated lags behind our knowledge in other repair pathways. The work carried out in this proposal will significantly improve our knowledge in this area providing significant insight for further human studies.