Sensor Mechanisms of HSF Activation

描述（由申请人提供）：热休克（HS）反应是对抗不利环境条件的主要细胞防御机制。HS反应的标志是HS基因的快速和稳健诱导，其中许多编码分子伴侣。热休克蛋白（Heat shock proteins，HSPs）也参与了多种病理过程，包括癌症、缺血/再灌注、炎症等。在真核生物中，HS基因的调控主要通过热休克转录因子（Heat shock transcription factors，HSFs）家族在转录水平进行，其中HSF 1是主要的调控因子。HSF 1在脊椎动物中作为无活性单体在严格的负调控下组成型表达。HSF 1的快速和稳健的翻译后激活响应于HS条件和其他应激源而发生。HSF 1的激活涉及DNA结合活性的三聚化和获得、磷酸化模式的改变和反式激活能力的获得。尽管进行了广泛的研究，但HSF 1激活的机制，特别是在三聚化步骤，仍然难以捉摸。在我们广泛的前期工作中，我们已经确定了两个对HSF 1激活至关重要的细胞因子：翻译延伸因子eEF 1A和一种称为HSR 1的新型大型非编码RNA。HSR 1被证明是作为一个细胞的温度传感器，而eEF 1A服务的蛋白质完整性的一般传感器。本提案的长期目标是提供一个全面的HSF 1激活和HSR 1/eEF 1A传感器机制的调节生理和机制的描述。具体而言，我们建议进行广泛的结构-功能表征的HSF 1-eEF 1A-HSR 1三元复合物和解开的机制HSF激活HSR 1/eEF 1A响应于哺乳动物和果蝇细胞中的各种类型的物理和化学应激。

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.