MECHANISM AND REGULATION OF SELENOPROTEIN SYNTHESIS

Abstract

Selenium is an essential trace element that is incorporated into proteins as selenocysteine (Sec), the twenty-first amino acid. Sec is encoded by a UGA codon in the selenoprotein mRNA. The decoding of UGA as Sec requires the reprogramming of translation because UGA is normally read as a stop codon. The translation of selenoprotein mRNAs requires cis-acting sequences in the mRNA and novel trans-acting factors dedicated to Sec incorporation. Selenoprotein synthesis in vivo is highly selenium-dependent, and there is a hierarchy of selenoprotein expression in mammals when selenium is limiting. This review describes emerging themes from studies on the mechanism, kinetics, and efficiency of Sec insertion in prokaryotes. Recent developments that provide mechanistic insight into how the eukaryotic ribosome distinguishes between UGA/Sec and UGA/stop codons are discussed. The efficiency and regulation of mammalian selenoprotein synthesis are considered in the context of current models for Sec insertion.

Selenoprotein expression is regulated at multiple levels in prostate cells

“…Selenium is incorporated as Sec at specific UGA codons in 25 human proteins (reviewed in [14][15][16]). Selenoprotein mRNAs all contain a cis-element within the 3' untranslated region (termed the Sec insertion sequence (SECIS) element) that is required for Sec incorporation.…”

Fontes orgânicas e inorgânicas de selênio na nutrição de vacas leiteiras: digestão, absorção, metabolismo e exigências

“…Para tal, o seleneto reage com ATP, formando selenofosfato, numa reação catalisada pela selenofosfato sintetase. A seguir, junto com um resíduo de serina, o selenofosfato forma uma SeCis, que é pós-translacionalmente inserida nas selenoproteínas funcionais através de um códon UGA específico (SUNDE & HOEKSTRA, 1980;DRISCOLL & COPELAND, 2003). A SeCis da dieta, por sua vez, não é incorporada diretamente em selenoproteínas funcionais, necessitando ser inicialmente reduzida a seleneto.…”

New Developments in Selenium Biochemistry: Selenocysteine Biosynthesis in Eukaryotes and Archaea

“…Several thorough reviews have covered these topics [1][2][3][4]. Herein, we have focused on recent developments involving the biosynthesis of selenocysteine (Sec) in eukaryotes and archaea that have not been reviewed elsewhere.…”

“…It is cotranslationally inserted into protein in response to the codon, UGA [1][2][3][4]. The biosynthesis of Sec occurs on its transfer RNA (tRNA), and the pathway begins with the initial aminoacylation of Sec tRNA with serine [5,6].…”