Recruitment of a SUMO isopeptidase to rDNA stabilizes silencing complexes by opposing SUMO targeted ubiquitin ligase activity.
Recruitment of a SUMO isopeptidase to rDNA stabilizes silencing complexes by opposing SUMO targeted ubiquitin ligase activity.
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DOI：
10.1101/gad.296145.117
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发表时间：
2017-04-15
影响因子：
10.5
通讯作者：
Zhou H
中科院分区：
文献类型：
--
作者：
Liang J;Singh N;Carlson CR;Albuquerque CP;Corbett KD;Zhou H
在这项研究中，Liang等人研究了SUMO（小泛素样修饰物）促进翻译后修饰的分子机制。他们的研究结果证明了本地化SUMO异肽酶和SUMO靶向泛素连接酶（STUbL）Slx 5：Slx 8的相反作用如何通过控制关键rDNA沉默蛋白Tof 2的丰度来调节rDNA沉默。SUMO（小泛素样修饰物）的翻译后修饰在真核细胞中起着重要但仍知之甚少的调节作用，包括作为SUMO靶向泛素连接酶（STUbL）泛素化的信号。在这里，我们描绘的SUMO依赖控制核糖体DNA（rDNA）沉默的分子机制，通过一个STUbL（Slx 5：Slx 8）和SUMO异肽酶（Ulp 2）的相反行动。我们确定了一个保守的区域在Ulp 2的C端介导其特异性的rDNA相关蛋白，并表明该区域直接结合到rDNA相关蛋白Csm 1。两个晶体结构表明，Csm 1相互作用与Ulp 2和它的底物之一，rDNA沉默蛋白Tof 2，通过其C-末端结构域中的相邻保守接口。破坏Csm 1与Ulp 2或Tof 2的相互作用显著降低了rDNA沉默，并导致Tof 2丰度显著下降，表明Ulp 2通过对抗STUbL介导的沉默蛋白降解来促进rDNA沉默。通过缺失STUbL SLX 5或破坏其SUMO相互作用基序来挽救Tof 2丰度，证实Tof 2以SUMO和STUbL依赖性方式被靶向降解。总体而言，我们的研究结果表明，本地化的SUMO异肽酶和STUbL的相反行动如何通过控制一个关键的rDNA沉默蛋白Tof 2的丰度来调节rDNA沉默。
In this study, Liang et al. investigate the molecular mechanisms by which SUMO (small ubiquitin-like modifier) contributes to post-translational modifications. Their findings demonstrate how the opposing actions of a localized SUMO isopeptidase and a SUMO targeted ubiquitin ligase (STUbL), Slx5:Slx8, regulate rDNA silencing by controlling the abundance of a key rDNA silencing protein, Tof2. Post-translational modification by SUMO (small ubiquitin-like modifier) plays important but still poorly understood regulatory roles in eukaryotic cells, including as a signal for ubiquitination by SUMO targeted ubiquitin ligases (STUbLs). Here, we delineate the molecular mechanisms for SUMO-dependent control of ribosomal DNA (rDNA) silencing through the opposing actions of a STUbL (Slx5:Slx8) and a SUMO isopeptidase (Ulp2). We identify a conserved region in the Ulp2 C terminus that mediates its specificity for rDNA-associated proteins and show that this region binds directly to the rDNA-associated protein Csm1. Two crystal structures show that Csm1 interacts with Ulp2 and one of its substrates, the rDNA silencing protein Tof2, through adjacent conserved interfaces in its C-terminal domain. Disrupting Csm1's interaction with either Ulp2 or Tof2 dramatically reduces rDNA silencing and causes a marked drop in Tof2 abundance, suggesting that Ulp2 promotes rDNA silencing by opposing STUbL-mediated degradation of silencing proteins. Tof2 abundance is rescued by deletion of the STUbL SLX5 or disruption of its SUMO-interacting motifs, confirming that Tof2 is targeted for degradation in a SUMO- and STUbL-dependent manner. Overall, our results demonstrate how the opposing actions of a localized SUMO isopeptidase and a STUbL regulate rDNA silencing by controlling the abundance of a key rDNA silencing protein, Tof2.