A heat shock transcription factor with reduced activity suppresses a yeast HSP70 mutant.
A heat shock transcription factor with reduced activity suppresses a yeast HSP70 mutant.
复制标题
活性降低的热休克转录因子抑制酵母 HSP70 突变体。
DOI：
10.1128/mcb.15.9.4890
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发表时间：
1995
影响因子：
5.3
通讯作者：
Craig,EA
中科院分区：
文献类型：
--
作者：
Halladay,JT;Craig,EA
同时携带酿酒酵母SSA1和SSA2 HSP70基因缺失的菌株表现出多效性，包括不能在37℃或更高的温度下生长，在允许的温度下生长速度降低，HSP基因表达增加，以及结构性耐热性。对thessa1 ssa2慢生长表型的基因外抑制基因的筛选发现了一个自发的显性抑制突变EXA3-1(R.J.Nelson，M.Heschl和E.A.Craig，Genetics 131：277-285,1992)。在此，我们报道EXA3-1是编码热休克转录因子(HSF)的HSF1的等位基因。在野生型背景中含有EXA3-1等位基因的菌株在稳态生长条件下HSF活性降低10-15倍，热休克后SSA4、HSP26和HSP104mRNAs的积累延迟。EXA3-1介导的抑制是HSF DNA结合域中高度保守的残基被单一氨基酸取代的结果，这大大降低了HSF与热休克元件结合的能力。综上所述，这些结果表明，ssa1和ssa2菌株的生长不良至少部分是由于一种有害的热休克蛋白(S)的过度生产造成的。这一结论得到了这样一个事实的支持，即含有EXA3-1等位基因的ssa2细胞至少部分热休克蛋白水平降低。令人惊讶的是，在野生型HSP70背景中含有EXA3-1等位基因的菌株在很宽的温度范围内的生长几乎与野生型菌株一样，在37℃时仅显示出轻微的生长速度下降，这表明细胞包含的HSF活性明显高于在稳定状态下生长所需的活性。
Strains carrying deletions in both theSSA1andSSA2 HSP70genes ofSaccharomyces cerevisiaeexhibit pleiotropic phenotypes, including the inability to grow at 37&C or higher, reduced growth rate at permissive temperatures, increasedHSPgene expression, and constitutive thermotolerance. A screen for extragenic suppressors of thessa1 ssa2slow-growth phenotype identified a spontaneous dominant suppressor mutation,EXA3-1(R. J. Nelson, M. Heschl, and E. A. Craig, Genetics 131:277–285, 1992). Here we report thatEXA3-1is an allele ofHSF1, which encodes the heat shock transcription factor (HSF). Strains containing theEXA3-1allele in a wild-type background exhibit a 10- to 15-fold reduction in HSF activity during steady-state growth conditions as well as a delay in the accumulation of theSSA4,HSP26, andHSP104mRNAs after a heat shock.EXA3-1-mediated suppression is the result of a single amino acid substitution of a highly conserved residue in the HSF DNA-binding domain which drastically reduces the ability of HSF to bind to heat shock elements as evaluated by band shift analysis. Together, these results indicate that the poor growth ofssa1 ssa2strains is the result, at least in part, of the overproduction of a deleterious heat shock protein(s). This conclusion is supported by the fact that the levels of at least some heat shock proteins are reduced inssa1 ssa2cells containing theEXA3-1allele. Surprisingly, strains containing theEXA3-1allele in a wild-typeHSP70background grow nearly as well as the wild-type strain over a wide temperature range, displaying only a slight reduction in growth rate at 37&C, indicating that cells contain significantly more HSF activity than is required for growth under steady-state conditions.