Hammack Lindsay J, Firestone Kyle, Chang William, Kusmierczyk Andrew R
Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA.
Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA.
Biochem Biophys Res Commun. 2017 Apr 29;486(2):438-443. doi: 10.1016/j.bbrc.2017.03.059. Epub 2017 Mar 18.
The eukaryotic 26S proteasome is a large protease comprised of two major sub assemblies, the 20S proteasome, or core particle (CP), and the 19S regulatory particle (RP). Assembly of the CP and RP is assisted by an expanding list of dedicated assembly factors. For the CP, this includes Ump1 and the heterodimeric Pba1-Pba2 and Pba3-Pba4 proteins. It is not known how many additional proteins that assist in proteasome biogenesis remain to be discovered. Here, we demonstrate that two members of the Hsp70 family in yeast, Ssa1 and Ssa2, play a direct role in CP assembly. Ssa1 and Ssa2 interact genetically and physically with proteasomal components. Specifically, they associate tightly with known CP assembly intermediates, but not with fully assembled CP, through an extensive purification protocol. And, in yeast lacking both Ssa1 and Ssa2, specific defects in CP assembly are observed.
真核生物的26S蛋白酶体是一种大型蛋白酶，由两个主要亚组件组成，即20S蛋白酶体或核心颗粒（CP）和19S调节颗粒（RP）。CP和RP的组装由越来越多的专门组装因子协助。对于CP来说，这包括Ump1以及异二聚体Pba1-Pba2和Pba3-Pba4蛋白。尚不清楚还有多少有助于蛋白酶体生物合成的其他蛋白质有待发现。在这里，我们证明酵母中Hsp70家族的两个成员Ssa1和Ssa2在CP组装中起直接作用。Ssa1和Ssa2在遗传和物理上与蛋白酶体成分相互作用。具体而言，通过广泛的纯化方案，它们与已知的CP组装中间体紧密结合，但不与完全组装的CP结合。并且，在同时缺乏Ssa1和Ssa2的酵母中，观察到CP组装存在特定缺陷。
