Sensor Mechanisms of HSF Activation

描述（由申请人提供）：热休克（HS）反应是细胞对不利环境条件的主要防御机制。HS反应的标志是HS基因的快速和强大的诱导，其中许多编码分子伴侣。热休克蛋白（HSPs）也涉及多种病理情况，包括癌症，缺血/再灌注，炎症等。在真核生物中，热休克基因的调控主要发生在转录水平上，由一系列热休克转录因子（hsf）调控，其中HSF1是主要调控因子。在严格的负调控下，HSF1作为无活性单体在脊椎动物中组成性表达。HSF1的快速和强大的翻译后激活发生在对HS条件和其他应激源的反应中。HSF1的激活包括三聚化和获得dna结合活性、磷酸化模式的改变和获得转激活能力。尽管有广泛的研究，HSF1的激活机制，特别是在三聚体化阶段，仍然是难以捉摸的。在我们广泛的初步工作中，我们已经确定了两个对HSF1激活至关重要的细胞因子：翻译延伸因子eEF1A和一种称为HSR1的新型大型非编码RNA。HSR1被证明是细胞热传感器，而eEF1A是蛋白质完整性的一般传感器。本提案的长期目标是提供HSF1激活及其通过HSR1/eEF1A传感器机制调控的全面生理和机制描述。具体而言，我们建议对HSF1-eEF1A- HSR1三元复合物进行广泛的结构-功能表征，并揭示HSR1/eEF1A在哺乳动物和果蝇细胞中响应各种物理和化学应激源时激活HSF的机制。

DESCRIPTION (provided by applicant): The heat shock (HS) response is the primary cellular defense mechanism against adverse environmental conditions. The hallmark of the HS response is the rapid and robust induction of HS genes, many of which encoding molecular chaperones. Heat shock proteins (HSPs) have been also implicated in a variety of pathological situations including cancer, ischemia/reperfusion, inflammation, etc. In eukaryotes the HS gene regulation occurs mainly at the transcriptional level by a family of heat shock transcription factors (HSFs), among which HSF1 is the master regulator. HSF1 is constitutively expressed in vertebrates as inactive monomer under tight negative regulation. Rapid and robust post- translational activation of HSF1 occurs in response to HS conditions and other stressors. Activation of HSF1 involves trimerization and acquisition of the DNA-binding activity, changes in phosphorylation pattern and acquisition of transactivation competence. Despite extensive research, the mechanism of HSF1 activation, especially at the trimerization step, remained elusive. During our extensive preliminary work we have identified two cellular factors that are essential for HSF1 activation: translation elongation factor eEF1A and a novel large non-coding RNA termed HSR1. HSR1 is shown to serve as a cellular thermosensor, whereas eEF1A serves a general sensor of protein integrity. The long-term objective of the present proposal is to provide a comprehensive physiological and mechanistic description of HSF1 activation and its regulation by HSR1/eEF1A sensor machinery. Specifically we propose to perform extensive structure-function characterization of HSF1-eEF1A- HSR1 ternary complex and unravel the mechanism underlying HSF activation by HSR1/eEF1A in response to various types of physical and chemical stressors in mammalian and Drosophila cells.