Phosphorylation of heat shock transcription factor in the stress response

所有生物体都通过改变转录程序和表达一组名为热休克蛋白(HSPs)的蛋白质来应对温度升高。在真核生物中，热休克转录因子(HSF)激活热休克蛋白基因的转录。HSF的靶基因含有一个被称为热休克元件的顺式作用序列。面包师的酵母，酿酒酵母，有一个由HSF1基因编码的HSF。在热休克条件下，HSFL蛋白被广泛的磷酸化，并获得更强的激活能力，尽管具体的调控机制尚不清楚。在这个项目中，我重点研究了HSFL的磷酸化和去磷酸化机制以及HSFL在各种胁迫反应中的作用。通过DNA微阵列分析，我们已经证明酵母HSFL是热诱导~70基因转录所必需的，目的基因编码分子伴侣和参与广泛生物学功能的蛋白质。我们已经鉴定了温度敏感的HSFL突变的多拷贝抑制基因，并发现HSFL与蛋白激酶Pkc1协同调节热休克反应中的细胞壁重塑。热诱导的HSFL过度磷酸化是大约一半的HSFL靶基因转录激活所必需的。这一要求与与HSE结合的HSFL三聚体之间的合作相互作用有关。与此一致，HSFL的寡聚化是应激诱导HSFL过度磷酸化的先决条件。我们还表明，人类HSF1识别HSE的方式与酵母Hsfl1略有不同。综上所述，这些结果表明HSE的结构是HSF-HSE相互作用的重要决定因素

All organisms respond to elevated temperatures by changing transcription programs and expressing a set of proteins called heat shock proteins (HSPs). In eukaryotes, heat sock transcription factor (HSF) activates transcription of HSP genes. The target genes of HSF contain a cis-acting sequence designated the heat shock element. The baker's yeast, Saccharomyces cerevisiae, has one HSF encoded by the HSF1 locus. Under heat shock condition, Hsfl protein is extensively phosphorylated and acquires a stronger activating ability, although detailed regulatory mechanisms remain unknown. In this project, I focused on mechanisms of Hsfl phosphorylation and dephosphorylation' and 'roles of Hsfl in the response to various stresses'.By using DNA microarray analysis, we have shown that yeast Hsfl is necessary for heat-induced transcription of〜70 genes and that target genes encode molecular chaperones and proteins involved in a broad range biological functions. We have characterized multicopy suppressor genes of a temperature-sensitive hsfl mutation and found that Hsfl in concert with a protein kinase Pkc1 regulates cell wall remodeling in response to heat shock. Heat-induced hyperphosphorylation of Hsfl was required for transcriptional activation of approximately half of Hsfl target genes. This requirement was related to cooperative interactions among Hsfl trimers bound to the HSE. Consistent with this, oligomerization of Hsfl was prerequisite for stress-induced hyperphosphorylation of Hsfl. We have also shown that human HSF1 recognizes HSEs in a slightly different way than yeast Hsfl.Taken together, these results suggest that the architecture of the HSE is an important determinant for HSF-HSE interactions