Yeast Nst1 is a novel component of P-bodies and is a specific suppressor of proteasome base assembly defects.
Yeast Nst1 is a novel component of P-bodies and is a specific suppressor of proteasome base assembly defects.
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DOI：
10.1091/mbc.e21-04-0178
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发表时间：
2021-10-01
影响因子：
3.3
通讯作者：
Hochstrasser M
中科院分区：
文献类型：
--
作者：
Cheng CL;Wong MK;Hochstrasser M
蛋白酶体组装利用多个专用组装伴侣，并受到响应不同应激条件的信号通路的调节。为了发现影响蛋白酶体碱基组装的新因素，我们筛选了平铺的高拷贝酵母基因组文库，以确定温度敏感的蛋白酶体调节颗粒（RP）碱基突变体的剂量抑制因子。筛选鉴定了负盐耐受性1（Nst 1），该蛋白在过表达时特异性抑制多碱基突变体的温度敏感性和蛋白酶体组装缺陷。在nas 6 Δ rpn 14 Δ细胞中，Nst 1过表达减少了细胞溶质RP ATP酶（Rpt）聚集体，该细胞缺乏两个RP组装分子伴侣。Nst 1是高度极性的，并预测有许多内在的无序区域，通常在蛋白质中发现的特征，可以分离成无膜缩合物。与此一致，内源性和过表达的Nst 1可以形成与加工体（P-体）组分共定位的胞质斑点。Nst 1过表达抑制了nas 6 Δ rpn 14 Δ细胞的整体蛋白翻译，这与P体中无活性mRNA的积累一致。已知翻译抑制在热应激下抑制碱基突变体中的聚集和蛋白酶体组装缺陷。我们的数据表明，Nst 1是一个以前被忽视的P-体组件，当表达水平升高时，抑制翻译，防止Rpt亚基聚集，并在应激条件下拯救蛋白酶体组装。
Proteasome assembly utilizes multiple dedicated assembly chaperones and is regulated by signaling pathways that respond to diverse stress conditions. To discover new factors influencing proteasome base assembly, we screened a tiled high-copy yeast genomic library to identify dosage suppressors of a temperature-sensitive proteasome regulatory particle (RP) base mutant. The screen identified negative salt tolerance 1 (Nst1), a protein that when overexpressed specifically suppressed the temperature sensitivity and proteasome-assembly defects of multiple base mutants. Nst1 overexpression reduced cytosolic RP ATPase (Rpt) aggregates in nas6Δ rpn14Δ cells, which lack two RP assembly chaperones. Nst1 is highly polar and predicted to have numerous intrinsically disordered regions, characteristics commonly found in proteins that can segregate into membraneless condensates. In agreement with this, both endogenous and overexpressed Nst1 could form cytosolic puncta that colocalized with processing body (P-body) components. Consistent with the accumulation of translationally inactive mRNAs in P-bodies, Nst1 overexpression inhibited global protein translation in nas6Δ rpn14Δ cells. Translational inhibition is known to suppress aggregation and proteasome assembly defects in base mutants under heat stress. Our data indicate that Nst1 is a previously overlooked P-body component that, when expressed at elevated levels inhibits translation, prevents Rpt subunit aggregation and rescues proteasome assembly under stress conditions.