Morano K A, Santoro N, Koch K A, Thiele D J
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA.
Mol Cell Biol. 1999 Jan;19(1):402-11. doi: 10.1128/MCB.19.1.402.
Gene expression in response to heat shock is mediated by the heat shock transcription factor (HSF), which in yeast harbors both amino- and carboxyl-terminal transcriptional activation domains. Yeast cells bearing a truncated form of HSF in which the carboxyl-terminal transcriptional activation domain has been deleted [HSF(1-583)] are temperature sensitive for growth at 37 degreesC, demonstrating a requirement for this domain for sustained viability during thermal stress. Here we demonstrate that HSF(1-583) cells undergo reversible cell cycle arrest at 37 degreesC in the G2/M phase of the cell cycle and exhibit marked reduction in levels of the molecular chaperone Hsp90. As in higher eukaryotes, yeast possesses two nearly identical isoforms of Hsp90: one constitutively expressed and one highly heat inducible. When expressed at physiological levels in HSF(1-583) cells, the inducible Hsp90 isoform encoded by HSP82 more efficiently suppressed the temperature sensitivity of this strain than the constitutively expressed gene HSC82, suggesting that different functional roles may exist for these chaperones. Consistent with a defect in Hsp90 production, HSF(1-583) cells also exhibited hypersensitivity to the Hsp90-binding ansamycin antibiotic geldanamycin. Depletion of Hsp90 from yeast cells wild type for HSF results in cell cycle arrest in both G1/S and G2/M phases, suggesting a complex requirement for chaperone function in mitotic division during stress.
热休克反应中的基因表达由热休克转录因子（HSF）介导，在酵母中，该因子同时具有氨基末端和羧基末端转录激活结构域。携带截短形式HSF（其中羧基末端转录激活结构域已缺失）的酵母细胞[HSF(1 - 583)]在37℃下生长对温度敏感，这表明在热应激期间持续存活需要该结构域。在此我们证明，HSF(1 - 583)细胞在37℃时在细胞周期的G2/M期经历可逆的细胞周期停滞，并且分子伴侣Hsp90的水平显著降低。与高等真核生物一样，酵母拥有两种几乎相同的Hsp90同工型：一种组成型表达，一种高度热诱导型。当在HSF(1 - 583)细胞中以生理水平表达时，由HSP82编码的可诱导Hsp90同工型比组成型表达的基因HSC82更有效地抑制了该菌株的温度敏感性，这表明这些伴侣蛋白可能存在不同的功能作用。与Hsp90产生缺陷一致，HSF(1 - 583)细胞对Hsp90结合的安莎霉素抗生素格尔德霉素也表现出超敏感性。从对HSF为野生型的酵母细胞中耗尽Hsp90会导致G1/S和G2/M期的细胞周期停滞，这表明在应激期间有丝分裂中伴侣蛋白功能存在复杂的需求。
