Selenoprotein H is a nucleolar thioredoxin-like protein with a unique expression pattern
Selenoprotein H is a nucleolar thioredoxin-like protein with a unique expression pattern
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DOI：
10.1074/jbc.m701605200
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发表时间：
2007-04-20
影响因子：
4.8
通讯作者：
Gladyshev, Vadim N.
中科院分区：
文献类型：
--
作者：
Novoselov, Sergey V.;Kryukov, Gregory V.;Gladyshev, Vadim N.
人类硒蛋白质组由 25 种已知的硒蛋白质组成，但其中许多蛋白质的功能尚不清楚。硒蛋白 H (SelH) 是最近发现的一种 14 kDa 哺乳动物蛋白，与功能性蛋白质没有序列同源性。通过灵敏的序列和结构分析，我们将 SelH 鉴定为硫氧还蛋白折叠样蛋白，其中保守的 CXXU 基序（由硒代半胱氨酸的其他两个残基分隔的半胱氨酸）对应于硫氧还蛋白中的 CXXC 基序。这些数据表明 SelH 具有氧化还原功能。事实上，重组 SelH 显示出显着的谷胱甘肽过氧化物酶活性。此外，SelH 在 N 端序列中具有保守的 RKRK 基序。我们在绿色荧光蛋白 (GFP) 的上游或下游克隆了 SelH 的野生型和半胱氨酸突变体形式，并将这种融合蛋白定位到转染的哺乳动物细胞的细胞核中，而 RKRK 基序的突变则产生了胞质蛋白。有趣的是，全长 SelH-GFP 融合蛋白特异性定位于核仁，而与 GFP 融合的 SelH 的 N 端序列具有弥散的核质位置。 Northern印迹分析显示，多种小鼠组织中SelH mRNA的表达水平较低，但在胚胎发育的早期阶段表达水平升高。此外，SelH mRNA 在人前列腺癌 LNCaP 和小鼠肺癌 LCC1 细胞中过表达。 RNA 干扰下调 SelH 使 LCC1 细胞对过氧化氢更敏感，但对其他测试的过氧化物不敏感。总体而言，这些数据表明 SelH 是一种新型核仁氧化还原酶，并表明该区室中的一些功能受氧化还原调节并依赖于微量元素硒。
The human selenoproteome consists of 25 known selenoproteins, but functions of many of these proteins are not known. Selenoprotein H ( SelH) is a recently discovered 14-kDa mammalian protein with no sequence homology to functionally characterized proteins. By sensitive sequence and structure analyses, we identified SelH as a thioredoxin fold-like protein in which a conserved CXXU motif ( cysteine separated by two other residues from selenocysteine) corresponds to the CXXC motif in thioredoxins. These data suggest a redox function of SelH. Indeed, a recombinant SelH shows significant glutathione peroxidase activity. In addition, SelH has a conserved RKRK motif in the N-terminal sequence. We cloned wild-type and cysteine mutant forms of SelH either upstream or downstream of green fluorescent protein ( GFP) and localized this fusion protein to the nucleus in transfected mammalian cells, whereas mutations in the RKRK motif resulted in the cytosolic protein. Interestingly, the full-length SelH-GFP fusion protein localized specifically to nucleoli, whereas the N-terminal sequence of SelH fused to GFP had a diffuse nucleoplasm location. Northern blot analyses revealed low expression levels of SelH mRNA in various mouse tissues, but it was elevated in the early stages of embryonic development. In addition, SelH mRNA was overexpressed in human prostate cancer LNCaP and mouse lung cancer LCC1 cells. Down-regulation of SelH by RNA interference made LCC1 cells more sensitive to hydrogen peroxide but not to other peroxides tested. Overall, these data establish SelH as a novel nucleolar oxidoreductase and suggest that some functions in this compartment are regulated by redox and dependent on the trace element selenium.