Structural Biology of XPB and XPD Helicases

描述(申请人提供)：DNA解旋酶XPB和XPD的遗传突变会导致不同表型的人类疾病，反映癌症增加或细胞死亡增加：着色性干皮病(XP)、XP连锁Cockayne综合征(CS)和毛硫代营养不良(TTD)。这些疾病反映了不同细胞通路的破坏：核苷酸切除修复缺陷(NER)导致XP，扰动转录偶联修复(TCR)导致CS，转录异常与NER缺陷共同导致TTD。在人类中，XPB和XPD解旋酶是TFIIH转录/修复复合体10个亚基的一部分，但致病突变聚集在XPB，特别是XPD，而不是TFB5以外的其他TFIIH蛋白中，因此这些XP解旋酶似乎是控制转录和修复协调的关键。此外，修复蛋白XPG和CSB与TCR中的XP解旋酶相互作用。然而，在分子水平上对XPB和XPD、它们的解旋酶和修复活性以及它们与TFB5、CSB和XPG的相互作用知之甚少。我们的目标是了解XPB和XPD解旋酶的特异性、活性、构象控制和途径协调的分子特征。我们的假设是，XPB和XPD解旋酶明确的结构、构象状态和分子界面为转录、NER和TCR提供了关键的控制。我们进一步提出，这些特征的特征及其被致病突变的破坏将提供直接将遗传基因突变与疾病表型联系起来的分子基础。为了验证这一点，我们在此建议将结构和生物物理实验(泰纳实验室)与生化和生物实验(库珀实验室)相结合。我们对XPB和XPD结构域和全长蛋白质、它们的古生物同源物以及它们的关键组件的实验将建立分子结构、构象转换机制和变构相互作用。我们希望表征一组典型的解旋酶结构，它们与DNA和蛋白质伙伴的复合体，并定义它们活动的关键相互作用。拟议的跨学科实验的预期结果是蛋白质-DNA复合体、蛋白质-蛋白质相互作用和功能状态的分子图像，这些功能状态协调由XPB和XPD作为TFIIH的组成部分介导的转录和修复事件。这些结果将有助于详细的分子理解与XPB、XPD、TFB5、CSB和XPG患者突变相关的癌症和细胞死亡疾病表型的基础过程。

DESCRIPTION (provided by applicant): Hereditary mutations in the DNA helicases XPB and XPD lead to human diseases with different phenotypes reflecting increased cancers or increased cell death: xeroderma pigmentosum (XP), XP- linked Cockayne syndrome (CS), and trichothiodystrophy (TTD). These diseases reflect the disruption of different cellular pathways: Defective nucleotide-excision repair (NER) results in XP, perturbed transcription-coupled repair (TCR) leads to CS, and transcription abnormalities combined with defective NER cause TTD. In humans, XPB and XPD helicases are part of the ten subunit TFIIH transcription/repair complex, but disease-causing mutations cluster in XPB and particularly XPD rather than in the other TFIIH proteins, excepting TFB5, so these XP helicases appear key to controlling coordination of transcription and repair. Furthermore, the repair proteins XPG and CSB interact with the XP helicases in TCR. However, there is little knowledge at the molecular level about XPB and XPD, their helicase and repair activities, or their interactions with TFB5, CSB and XPG. We aim to understand the molecular features underlying the specificity, activity, conformational controls and pathway coordination by the XPB and XPD helicases. Our hypothesis is that well-defined architectures, conformational states, and molecular interfaces of XPB and XPD helicases provide critical controls for transcription, NER, and TCR. We furthermore propose that characterizations of these features and their disruption by disease-causing mutations will provide a molecular basis to directly connect the inherited gene mutations to disease phenotypes. To test this, we herein propose to integrate structural and biophysical experiments (Tainer laboratory) with biochemical and biological experiments (Cooper laboratory). Our experiments on XPB and XPD domains and full-length proteins, their archaeal homologues, and their key assemblies will establish molecular architectures, conformational switching mechanisms, and allosteric interactions. We expect to characterize a prototypical set of helicase structures, their complexes with DNA and with protein partners, and to define the key interactions for their activities. The anticipated outcome of the proposed cross-disciplinary experiments is a molecular picture of the protein-DNA complexes, protein-protein interactions and functional states that orchestrate transcription and repair events mediated by XPB and XPD as components of TFIIH. These results will help provide a detailed molecular understanding of the processes that underlie the cancer and cell death disease phenotypes associated with XPB, XPD, TFB5, CSB and XPG patient mutations.