Suppression of an Hsp70 mutant phenotype in Saccharomyces cerevisiae through loss of function of the chromatin component Sin1p/Spt2p
Suppression of an Hsp70 mutant phenotype in Saccharomyces cerevisiae through loss of function of the chromatin component Sin1p/Spt2p
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DOI：
10.1128/jb.180.24.6484-6492.1998
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发表时间：
1998-12-01
影响因子：
3.2
通讯作者：
Craig, EA
中科院分区：
文献类型：
--
作者：
Baxter, BK;Craig, EA
酿酒酵母中Hsp70分子伴侣的SSA亚家族有4个成员，分别由SSA1、SSA2、SSA3和SSA4编码。两个结构性表达基因SSA1和SSA2的缺失导致细胞生长缓慢和对温度敏感。在这项研究中，我们证明了ssa1 ssa2菌株温度敏感性的基因外抑制因子EXA1-1是SIN1/SPT2的功能缺失突变，SIN1/SPT2编码染色质的非组蛋白成分。Sin1p功能的丧失导致SSA3在ssa1 ssa2突变背景中过表达，达到足以介导抑制的水平。在一株SSA基因的野生型菌株中，除了在热休克条件下，我们没有检测到Sin1p对Ssa3p表达的影响。现有数据表明，SSA3在ssa1、ssa2突变背景和热休克野生型菌株中的表达是由热休克转录因子HSF介导的。我们的研究结果表明，SSA3的诱导是由HSF介导的，而SSA3受Sin1p的调控。因此，EXA1-1抑制突变通过选择性地增加HSF介导的SSA3的表达来促进ssa1 ssa2菌株的生长。
The Ssa subfamily of Hsp70 molecular chaperones in the budding yeast Saccharomyces cerevisiae has four members, encoded by SSA1, SSA2, SSA3, and SSA4. Deletion of the two constitutively expressed genes, SSA1 and SSA2, results in cells which are slow growing and temperature sensitive. In this study, we demonstrate that an extragenic suppressor of the temperature sensitivity of ssa1 ssa2 strains, EXA1-1, is a loss-of-function mutation in SIN1/SPT2, which encodes a nonhistone component of chromatin. Loss of function of Sin1p leads to overexpression of SSA3 in the ssa1 ssa2 mutant background, at a level which is sufficient to mediate suppression. In a strain which is wild type for SSA genes, we detected no effect of Sin1p on Ssa3p expression except under conditions of heat shock. Existing data indicate that expression of SSA3 in the ssa1 ssa2 mutant background as well as in heat-shocked wild-type strains is mediated by the heat shock transcription factor HSF. Our findings suggest that it is HSF-mediated induction of SSA3 which is modulated by Sin1p. The EXA1-1 suppressor mutation thus improves the growth of ssa1 ssa2 strains by selectively increasing HSF-mediated expression of SSA3.