Latent effects of Hsp90 mutants revealed at reduced expression levels.
Latent effects of Hsp90 mutants revealed at reduced expression levels.
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DOI：
10.1371/journal.pgen.1003600
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发表时间：
2013-06
期刊：
影响因子：
4.5
通讯作者：
Bolon DN
中科院分区：
文献类型：
--
作者：
Jiang L;Mishra P;Hietpas RT;Zeldovich KB;Bolon DN
在自然系统中，选择作用于蛋白质序列和表达水平，但尚不清楚选择如何整合这两个维度。我们最近开发的EMPIRIC方法，系统地确定所有可能的点突变体的重要区域的必需基因在酵母中的健身效果。在这里，我们系统地研究了在一个假定的底物结合环的酵母热休克蛋白90（热休克蛋白82）在广泛的表达强度的点突变的健身效果。降低的表达强度和氨基酸取代之间的负上位性是常见的，内源性表达强度经常掩盖突变缺陷。通过分析不同表达强度下的适应性效应，我们能够揭示所有突变体对功能的影响。大多数突变体引起部分功能缺陷，与Hsp90的该区域有助于突变敏感和关键过程一致。这些结果表明，蛋白质的重要功能区域可以容忍突变缺陷，而不会对适应性产生实验观察到的影响。蛋白质序列或表达强度的变化都可以导致自然系统的适应。虽然许多研究分别集中在表达强度或蛋白质序列上，但原则上这两种蛋白质性质的适应性效应是相互依赖的。我们系统地研究了酵母Hsp90基因（Hsp82）的表达强度和蛋白质序列的适应性效应。我们分析了七种不同表达强度下，假定底物结合环中所有可能的点突变的适应性效应。氨基酸替换的适应性效应强烈依赖于表达强度。许多点突变在降低的表达强度下表现出隐藏在天然表达强度下的适应性缺陷。揭示这些隐藏的突变缺陷表明，这一地区的热休克蛋白90有助于限速步骤的功能，与其在底物结合的假定作用一致。这项研究很重要，因为它表明蛋白质中的关键区域比基于在自然表达强度下进行的实验适应性分析所估计的更普遍。由于隐藏的适应性效应可能发生在其他系统中，这些发现对实验进化领域具有广泛的影响。
In natural systems, selection acts on both protein sequence and expression level, but it is unclear how selection integrates over these two dimensions. We recently developed the EMPIRIC approach to systematically determine the fitness effects of all possible point mutants for important regions of essential genes in yeast. Here, we systematically investigated the fitness effects of point mutations in a putative substrate binding loop of yeast Hsp90 (Hsp82) over a broad range of expression strengths. Negative epistasis between reduced expression strength and amino acid substitutions was common, and the endogenous expression strength frequently obscured mutant defects. By analyzing fitness effects at varied expression strengths, we were able to uncover all mutant effects on function. The majority of mutants caused partial functional defects, consistent with this region of Hsp90 contributing to a mutation sensitive and critical process. These results demonstrate that important functional regions of proteins can tolerate mutational defects without experimentally observable impacts on fitness. Changes in protein sequence or expression strength can both lead to adaptation in natural systems. While many studies have focused individually on either expression strength or protein sequence, in principle the fitness effects of these two protein properties are interdependent. We systematically investigated the fitness effects of both expression strength and protein sequence for the yeast Hsp90 gene (Hsp82). We analyzed the fitness effects of all possible point mutations in a putative substrate binding loop under seven different expression strengths. The fitness effects of amino acid substitutions were strongly dependent on expression strength. Many point mutations exhibited fitness defects at reduced expression strength that were hidden at the natural expression strength. Revealing these hidden mutant defects suggested that this region of Hsp90 contributes to a rate-limiting step in function, consistent with its putative role in substrate binding. This study is important because it indicates that critical regions in proteins are more prevalent than would be estimated based on experimental fitness analyses performed at natural expression strengths. As hidden fitness effects are likely to occur in other systems, these findings have broad implications for the field of experimental evolution.
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影响因子：
14.8
作者：
Hietpas, Ryan;Roscoe, Benjamin;Jiang, Li;Bolon, Daniel N. A.
通讯作者：
Bolon, Daniel N. A.
DOI：
10.1073/pnas.89.22.10915
发表时间：
1992-11-15
影响因子：
11.1
作者：
HENIKOFF, S;HENIKOFF, JG
通讯作者：
HENIKOFF, JG
影响因子：
3.9
作者：
KACSER, H;BURNS, JA;FELL, DA
通讯作者：
FELL, DA
影响因子：
5.7
作者：
Adkar, Bharat V.;Tripathi, Arti;Varadarajan, Raghavan
通讯作者：
Varadarajan, Raghavan
影响因子：
64.8
作者：
Dekel, E;Alon, U
通讯作者：
Alon, U