Satyal S H, Chen D, Fox S G, Kramer J M, Morimoto R I
Department of Biochemistry, Molecular Biology and Cell Biology, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois 60208 USA.
Genes Dev. 1998 Jul 1;12(13):1962-74. doi: 10.1101/gad.12.13.1962.
In response to stress, heat shock factor 1 (HSF1) acquires rapid DNA binding and transient transcriptional activity while undergoing conformational transition from an inert non-DNA-binding monomer to active functional trimers. Attenuation of the inducible transcriptional response occurs during heat shock or upon recovery at non-stress conditions and involves dissociation of the HSF1 trimer and loss of activity. We have used the hydrophobic repeats of the HSF1 trimerization domain in the yeast two-hybrid protein interaction assay to identify heat shock factor binding protein 1 (HSBP1), a novel, conserved, 76-amino-acid protein that contains two extended arrays of hydrophobic repeats that interact with the HSF1 heptad repeats. HSBP1 is nuclear-localized and interacts in vivo with the active trimeric state of HSF1 that appears during heat shock. During attenuation of HSF1 to the inert monomer, HSBP1 associates with Hsp70. HSBP1 negatively affects HSF1 DNA-binding activity, and overexpression of HSBP1 in mammalian cells represses the transactivation activity of HSF1. To establish a biological role for HSBP1, the homologous Caenorhabditis elegans protein was overexpressed in body wall muscle cells and was shown to block activation of the heat shock response from a heat shock promoter-reporter construct. Alteration in the level of HSBP1 expression in C. elegans has severe effects on survival of the animals after thermal and chemical stress, consistent with a role for HSBP1 as a negative regulator of the heat shock response.
在应激反应中，热休克因子1（HSF1）获得快速的DNA结合能力和瞬时转录活性，同时经历从无活性的非DNA结合单体到有活性的功能性三聚体的构象转变。诱导型转录反应在热休克期间或在非应激条件下恢复时减弱，涉及HSF1三聚体的解离和活性丧失。我们利用酵母双杂交蛋白相互作用试验中HSF1三聚化结构域的疏水重复序列，鉴定出热休克因子结合蛋白1（HSBP1），这是一种新的、保守的、由76个氨基酸组成的蛋白质，它包含两个与HSF1七肽重复序列相互作用的疏水重复序列延伸阵列。HSBP1定位于细胞核，在体内与热休克期间出现的HSF1活性三聚体状态相互作用。在HSF1衰减为无活性单体的过程中，HSBP1与Hsp70结合。HSBP1对HSF1的DNA结合活性产生负面影响，在哺乳动物细胞中过表达HSBP1会抑制HSF1的反式激活活性。为了确定HSBP1的生物学作用，将同源的秀丽隐杆线虫蛋白在体壁肌肉细胞中过表达，结果显示它能阻断热休克启动子-报告基因构建体的热休克反应激活。秀丽隐杆线虫中HSBP1表达水平的改变对动物在热应激和化学应激后的存活有严重影响，这与HSBP1作为热休克反应负调节因子的作用一致。
