HSP90 interacts with and regulates the activity of heat shock factor 1 in Xenopus oocytes
HSP90 interacts with and regulates the activity of heat shock factor 1 in Xenopus oocytes
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DOI：
10.1128/mcb.18.9.4949
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发表时间：
1998-09-01
影响因子：
5.3
通讯作者：
Ovsenek, N
中科院分区：
文献类型：
--
作者：
Ali, A;Bharadwaj, S;Ovsenek, N
热休克基因的转录激活是一个可逆的多步骤过程，包括将失活的热休克因子1（HSF 1）单体转化为热休克元件（HSE）结合的同源三聚体，过度磷酸化，以及诱导完全转录能力的进一步修饰。HSF 1受多种调节机制控制，包括被额外的细胞因子抑制、与HSP 70的物理相互作用以及整合到不同的细胞信号级联中。然而，细胞响应应激和控制HSF 1激活-失活途径的信号传导机制尚不清楚。在这里，我们表明，HSP 90，细胞伴侣已知的调节几个信号转导分子和转录因子，在HSF 1的调节功能。HSP 90抗体（Abs）在体外识别HSF 1-HSE复合物，HSP 90抗体直接注射入卵母细胞核内在体内识别HSF 1。通过使用两种策略分析HSP 90-HSF 1相互作用的功能影响：直接核注射HSP 90 Abs和用格尔德霉素（GA）处理细胞，格尔德霉素是一种特异性阻断HSP 90的伴侣活性的试剂。热休克蛋白90抗体和GA都延迟了热休克恢复过程中HSF 1三聚体的解体，并特异性抑制热诱导的氯霉素乙酰转移酶报告基因构建体在热休克蛋白70启动子控制下的转录。在无热休克条件下，HSP 90抗体激活HSE结合，这种作用可被随后注射纯化的HSP 90逆转。GA在非休克条件下不激活HSE结合，但增加热休克诱导的HSE结合量。基于这些发现和已知的HSP 90的特性，我们提出了一个新的调控模型，其中HSP 90参与调节HSF 1在不同的点沿着激活-失活途径，影响单体和三聚体构象之间的相互转换以及转录激活。我们还提出了HSP 90将HSF 1与协调应激反应的细胞信号分子联系起来的假设。
Transcriptional activation of heat shock genes is a reversible and multistep process involving conversion of inactive heat shock factor 1 (HSF1) monomers into heat shock element (HSE)-binding homotrimers, hyperphosphorylation, and further modifications that induce full transcriptional competence. HSF1 is controlled by multiple regulatory mechanisms, including suppression by additional cellular factors, physical interactions with HSP70, and integration into different cellular signaling cascades. However, the signaling mechanisms by which cells respond to stress and control the HSF1 activation-deactivation pathway are not known. Here we demonstrate that HSP90, a cellular chaperone known to regulate several signal transduction molecules and transcription factors, functions in the regulation of HSF1. The existence of HSF1-HSP90 heterocomplexes was shown by coimmunoprecipitation of HSP90 with HSF1 from unshocked and heat-shocked nuclear extracts, recognition of HSF1-HSE complexes in vitro by using HSP90 antibodies (Abs), and recognition of HSF1 in vivo by HSP90 Abs microinjected directly into oocyte nuclei. The functional impact of HSP90-HSF1 interactions was analyzed by using two strategies: direct nuclear injection of HSP90 Abs and treatment of cells with geldana-mycin (GA), an agent that specifically blocks the chaperoning activity of HSP90. Both HSP90 Abs and GA delayed the disassembly of HSF1 trimers during recovery from heat shock and specifically inhibited heat-induced transcription from a chloramphenicol acetyltransferase reporter construct under control of the hsp70 promoter. HSP90 Abs activated HSE binding in the absence of heat shock, an effect that could be reversed by subsequent injection of purified HSP90, GA did not activate HSE binding under nonshock conditions but increased the quantity of HSE binding induced by heat shock. On the basis of these findings and the known properties of HSP90, we propose a new regulatory model in which HSP90 participates in modulating HSF1 at different points along the activation-deactivation pathway, influencing the interconversion between monomeric and trimeric conformations as well as transcriptional activation. We also put forth the hypothesis that HSP90 links HSF1 to cellular signaling molecules coordinating the stress response.