Monosome Formation during Translation Initiation Requires the Serine/Arginine-Rich Protein Npl3
Monosome Formation during Translation Initiation Requires the Serine/Arginine-Rich Protein Npl3
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DOI：
10.1128/mcb.00873-13
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发表时间：
2013-12-01
影响因子：
5.3
通讯作者：
Krebber, Heike
中科院分区：
文献类型：
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作者：
Baierlein, Claudia;Hackmann, Alexandra;Krebber, Heike
富含丝氨酸/丝氨酸的酵母穿梭蛋白Np 13是mRNA和前60 S核糖体亚基从细胞核输出到细胞质所必需的。在这里，我们报道了Npl 3在翻译起始中的新功能。阻止其二聚化的C末端突变（npl 3 Delta 100）对细胞是致命的，并导致翻译缺陷，如[S-35]甲硫氨酸掺入测定和对翻译抑制剂放线菌酮的超敏反应所示。此外，该Npl 3突变体在多聚体谱中显示出半聚体，这指示了单体形成中的缺陷。引人注目的是，Npl 3二聚化能力的丧失不影响mRNA和前60 S输出。事实上，npl 3 Delta 100和野生型Npl 3的mRNA和rRNA结合能力相似。有趣的是，Npl 3的二聚化结构域的过表达干扰二聚体形成并导致显性负效应，反映在生长缺陷和半聚体形成表型中。此外，我们发现了与核糖体亚基连接因子Rpl 10和真核生物翻译起始因子5 B/Fun 12的特异性遗传相互作用，并检测到npl 3 Delta 100与含Rpl 10复合物的结合显著降低。这些发现表明Npl 3在细胞质中的基本新功能，其支持用于翻译起始的单体形成。
The yeast shuttling serine/arginine-rich protein Npl3 is required for the export of mRNAs and pre-60S ribosomal subunits from the nucleus to the cytoplasm. Here, we report a novel function of Npl3 in translation initiation. A mutation in its C terminus that prevents its dimerization (npl3 Delta 100) is lethal to cells and leads to translational defects, as shown by [S-35] methionine incorporation assays and a hypersensitivity to the translational inhibitor cycloheximide. Moreover, this Npl3 mutant shows halfmers in polysomal profiles that are indicative of defects in monosome formation. Strikingly, the loss of the ability of Npl3 to dimerize does not affect mRNA and pre-60S export. In fact, the mRNA and rRNA binding capacities of npl3 Delta 100 and wild-type Npl3 are similar. Intriguingly, overexpression of the dimerization domain of Npl3 disturbs dimer formation and results in a dominant-negative effect, reflected in growth defects and a halfmer formation phenotype. In addition, we found specific genetic interactions with the ribosomal subunit joining factors Rpl10 and eukaryotic translation initiation factor 5B/Fun12 and detected a substantially decreased binding of npl3 Delta 100 to the Rpl10-containing complex. These findings indicate an essential novel function for Npl3 in the cytoplasm, which supports monosome formation for translation initiation.