Mechanism of selenoprotein synthesis

描述（由申请人提供）：硒蛋白是氨基酸硒半胱氨酸与UGA密码子共译结合的蛋白质。在过去的十年里，对硒蛋白的研究主要集中在两个方面：鉴定新的硒蛋白和阐明其功能，以及揭示细胞翻译机制指导该氨基酸在“停止”密码子上的结合机制。在她的博士后研究期间，研究者首次发现了mrna中赋予硒代半胱氨酸结合的信号，称为SECIS元件。最近发现了介导硒代半胱氨酸掺入的两个因子EFsec和SBP2。我们的实验室鉴定并表征了硒半胱氨酸- trna特异性延伸因子EFsec，该因子通过与SECIS结合蛋白SBP2相互作用介导这种不寻常氨基酸的结合。我们还证明了EFsec与SBP2的相互作用，以及硒半胱氨酸- trna在介导这种相互作用中的作用。其他因子也参与了这一过程，包括两个功能未知的因子，SECp43和SLA/LP，以及两个功能已知的因子，硒磷酸合成酶和硒半胱氨酸裂解酶。我们正在表达和表征这些蛋白质，目的是了解它们如何介导硒代半胱氨酸的生物合成和结合到蛋白质中。要解决的具体目标是：

DESCRIPTION (provided by applicant): Selenoproteins are proteins in which the amino acid, selenocysteine, is incorporated cotranslationally at UGA codons. Studies of selenoproteins over the last decade or so have focused on two major areas, identification of new selenoproteins and elucidation of their functions, and unraveling the mechanism by which the cellular translational machinery directs incorporation of this amino acid at a "stop" codon. The signals in mRNAs conferring selenocysteine incorporation, termed SECIS elements, were first identified by the investigator during her postdoctoral studies. Recently, two factors that mediate selenocysteine incorporation were identified, EFsec and SBP2. Our laboratory identified and is characterizing the selenocysteyl-tRNA specific elongation factor, EFsec, which mediates incorporation of this unusual amino acid, through interaction with the SECIS binding protein, SBP2. We have also demonstrated interaction of EFsec with SBP2, and the role of selenocysteyl-tRNA in mediating this interaction. Other factors have been implicated in this process, including two of unknown function, SECp43 and SLA/LP, and two of known function, selenophosphate synthase and selenocysteine lyase. We are expressing and characterizing these proteins with the goal of understanding how they function to mediate selenocysteine biosynthesis and incorporation into proteins. Specific aims to be addressed are: I. Investigate functions of SECp43, SLA/LP and selenocysteine lyase in selenoprotein synthesis. II. Investigate subcellular localization and nucleocytoplasmic transport of EFsec and SBP2, and the implications for nonsense mediated decay and the hierarchy of selenoprotein synthesis. III. Investigate interactions between EFsec, SBP2 and their interaction partners, and the functions of these interaction partners in selenoprotein synthesis.