Dietary selenium affect methylation of the wobble nucleoside in the anticodon of selenocysteine tRNA[Ser]Sec

• Published in: The Journal of biological chemistry Vol. 268; no. 19
• Main Authors: Diamond, A.M, Choi, I.S, Crain, P.F, Hashizume, T, Pomerantz, S.C, Cruz, R, Steer, C.J, Hill, K.E, Burk, R.F, McCloskey, J.A, Hatfield, D.L
• Format: Journal Article
• Language: English
• Published: 05-07-1993
• Subjects: ACIDE AMINE; AMINOACIDOS; ARN DE TRANSFERENCIA; ARN DE TRANSFERT; CARENCE EN OLIGOELEMENT; CARENCE MINERALE; CISTEINA; CYSTEINE; DEFICIENCIA DE MINERALES; DEFICIENCIA DE OLIGOELEMENTOS; DIETA; METHYLATION; METILACION; MINERALES; MINERAUX; NUCLEOSIDE; NUCLEOSIDOS; RAT; RATA; REGIME ALIMENTAIRE; SELENIO; SELENIUM
• ISSN: 0021-9258; 1083-351X

We reported previously that the presence of selenium in culture media of mammalian cells influences both the steady-state levels and distributions of two tRNA isoacceptors involved in the insertion of selenocysteine into protein in response to certain UGA codons. In this study, we demonstrate an increase in the levels of these isoacceptors in rats fed a selenium-adequate diet compared to animals fed a selenium-deficient diet, as well as a shift in the relative distribution toward the tRNA which elutes later from an RPC-5 column. These effects were found to occur in a tissue-specific manner. Both selenoeysteine tRNAs were isolated from rat liver, sequenced, analyzed by mass spectrometry, and shown to differ only by ribose 2'-O-methylation of 5- methylcarboxymethyluridine that occurs in the wobble position of the anticodon. This modified nucleoside has been documented previously only in yeast tRNA while the corresponding 2'-O-methylribose derivative has not been observed. The structure of these nucleosides was established by mass spectrometry and confirmed by chemical synthesis. Although the role of methylation of the wobble nucleotide is not known, the differences in elution properties from RPC-5 columns are consistent with other experimental observations indicating that a change in tRNA conformation accompanies this methylation