Supramolecular complexes mediate selenocysteine incorporation in vivo
Supramolecular complexes mediate selenocysteine incorporation in vivo
复制标题
DOI：
10.1128/mcb.26.6.2337-2346.2006
复制
发表时间：
2006-03-01
影响因子：
5.3
通讯作者：
Berry, MJ
中科院分区：
文献类型：
--
作者：
Small-Howard, A;Morozova, N;Berry, MJ
真核生物中的硒代半胱氨酸掺入通过RNA-蛋白质复合物的相互作用在UGA密码子处协同发生，一种由硒代半胱氨酸（Sec）-tRNA（[Ser]Sec）及其特异性延伸因子EFsec组成，另一种由SECIS元件和SECIS结合蛋白SBP 2组成。参与该途径的其他因子包括两种硒磷酸合成酶，SPS 1和SPS 2，核糖体蛋白L30，Sec和两种被鉴定为结合IRNA（[Ser]Sec）的因子，称为可溶性肝抗原/肝蛋白（SLA/LP）和SECp 43。我们报告SLA/LP：和SPS 1在体外和体内相互作用，SECp 43共转染增加了这种相互作用，并重新分配所有三种蛋白质的主要核定位。我们进一步表明，SECp 43相互作用的硒半胱氨酸-tRNA（[Ser]Sec）-EFsec复合物在体外，和SECp 43共表达促进EFsec和SBP 2在体内之间的相互作用。此外，SECp 43增加硒代半胱氨酸掺入和硒蛋白mRNA水平，后者可能是由于规避无义介导的衰变。因此，SECp 43成为协调硒蛋白生物合成中涉及的其他因子的相互作用和定位的关键参与者。最后，我们的研究描绘了SECp 43和先前描述的硒蛋白共翻译因子之间的多个，协调的蛋白质-核酸相互作用，导致硒代半胱氨酸的生物合成和掺入依赖于细胞质和核的超分子复合物的模型。
Selenocysteine incorporation in eukaryotes occurs cotranslationally at UGA codons via the interactions of RNA-protein complexes, one comprised of selenocysteyl (Sec)-tRNA([Ser]Sec) and its specific elongation factor, EFsec, and another consisting of the SECIS element and SECIS binding protein, SBP2. Other factors implicated in this pathway include two selenophosphate synthetases, SPS1 and SPS2, ribosomal protein L30, Sec and two factors identified as binding IRNA([Ser]Sec), termed soluble liver antigen/liver protein (SLA/LP) and SECp43. We report that SLA/LP :and SPS1 interact in vitro and in vivo and that SECp43 cotransfection increases this interaction and redistributes all three proteins to a predominantly nuclear localization. We further show that SECp43 interacts with the selenocysteyl-tRNA([Ser]Sec)-EFsec complex in vitro, and SECp43 coexpression promotes interaction between EFsec and SBP2 in vivo. Additionally, SECp43 increases selenocysteine incorporation and selenoprotein mRNA levels, the latter presumably due to circumvention of nonsense-mediated decay. Thus, SECp43 emerges as a key player in orchestrating the interactions and localization of the other factors involved in selenoprotein biosynthesis. Finally, our studies delineating the multiple, coordinated protein-nucleic acid interactions between SECp43 and the previously described selenoprotein cotranslational factors resulted in a model of selenocysteine biosynthesis and incorporation dependent upon both cytoplasmic and nuclear supramolecular complexes.