Role of the ubiquitin-like protein Urm1 as a noncanonical lysine-directed protein modifier
Role of the ubiquitin-like protein Urm1 as a noncanonical lysine-directed protein modifier
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DOI：
10.1073/pnas.1014402108
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发表时间：
2011-02-01
影响因子：
11.1
通讯作者：
Jentsch, Stefan
中科院分区：
文献类型：
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作者：
Van der Veen, Annemarthe G.;Schorpp, Kenji;Jentsch, Stefan
泛素(Ub)相关修饰物Urm1在tRNA硫化反应中作为硫载体发挥作用，其机制需要在Urm1的C-末端甘氨酸残基形成硫羧酸盐。然而，Urm1是否作为Ub样蛋白修饰物发挥了额外作用仍不清楚。在这里，我们证明了Urm1与目标蛋白质的赖氨酸残基结合，氧化应激促进了酿酒酵母和哺乳动物细胞中蛋白质的熊果化。与泛素化类似，熊果化涉及硫酯中间体，并导致Urm1与其底物之间形成共价肽键。然而，与典型的类Ub修饰剂的修饰相反，Urm1的结合涉及修饰剂的C-末端硫代羧酸盐。我们已经证实，在酿酒酵母中，过氧化还蛋白Ahp1就是这样的底物，并发现Urm1在体内针对Ahp1的特定赖氨酸残基。此外，我们已经在哺乳动物细胞中确定了几种独特的底物，并表明Urm1至少针对氧化剂处理的两条途径。首先，Urm1被附加到三种成分的赖氨酸残基上，这三种成分在其自身的途径中发挥作用(即MOCS3、ATPBD3和CTU2)。第二，Urm1与核质穿梭因子细胞凋亡易感性蛋白偶联。因此，Urm1通过整合原核硫载体和Ub家族的真核蛋白修饰物的功能，具有保守的双重作用。
The ubiquitin (Ub)-related modifier Urm1 functions as a sulfur carrier in tRNA thiolation by means of a mechanism that requires the formation of a thiocarboxylate at the C-terminal glycine residue of Urm1. However, whether Urm1 plays an additional role as a Ub-like protein modifier remains unclear. Here, we show that Urm1 is conjugated to lysine residues of target proteins and that oxidative stress enhances protein urmylation in both Saccharomyces cerevisiae and mammalian cells. Similar to ubiquitylation, urmylation involves a thioester intermediate and results in the formation of a covalent peptide bond between Urm1 and its substrates. In contrast to modification by canonical Ub-like modifiers, however, conjugation of Urm1 involves a C-terminal thiocarboxylate of the modifier. We have confirmed that the peroxiredoxin Ahp1 is such a substrate in S. cerevisiae and found that Urm1 targets a specific lysine residue of Ahp1 in vivo. In addition, we have identified several unique substrates in mammalian cells and show that Urm1 targets at least two pathways on oxidant treatment. First, Urm1 is appended to lysine residues of three components that function in its own pathway (i.e., MOCS3, ATPBD3, and CTU2). Second, Urm1 is conjugated to the nucleocytoplasmic shuttling factor cellular apoptosis susceptibility protein. Thus, Urm1 has a conserved dual role by integrating the functions of prokaryotic sulfur carriers with those of eukaryotic protein modifiers of the Ub family.