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Methylation of the ribosyl moiety at position 34 of selenocysteine tRNA[Ser]Sec is governed by both primary and tertiary structure

Published online by Cambridge University Press:  01 September 2000

LARK KYUN KIM ,
TAMIKO MATSUFUJI ,
SENYA MATSUFUJI ,
BRADLEY A. CARLSON ,
SUKWON S. KIM ,
DOLPH L. HATFIELD  and
BYEONG JAE LEE
LARK KYUN KIM
Affiliation:
Laboratory of Molecular Genetics, Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea
TAMIKO MATSUFUJI
Affiliation:
Department of Internal Medicine (Daisan Hospital), Jikei University School of Medicine, Tokyo 105-8461, Japan
SENYA MATSUFUJI
Affiliation:
Department of Biochemistry II, Jikei University School of Medicine, Tokyo 105-8461, Japan
BRADLEY A. CARLSON
Affiliation:
Basic Research Laboratory, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
SUKWON S. KIM
Affiliation:
Laboratory of Molecular Genetics, Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea
DOLPH L. HATFIELD
Affiliation:
Basic Research Laboratory, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
BYEONG JAE LEE
Affiliation:
Laboratory of Molecular Genetics, Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea
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Abstract

The selenocysteine (Sec) tRNA[Ser]Sec population in higher vertebrates consists of two major isoacceptors that differ from each other by a single nucleoside modification in the wobble position of the anticodon (position 34). One isoacceptor contains 5-methylcarboxymethyluridine (mcmU) in this position, whereas the other contains 5-methylcarboxymethyluridine-2′-O-methylribose (mcmUm). The other modifications in these tRNAs are N6-isopentenyladenosine (i6A), pseudouridine (ψ), and 1-methyladenosine (m1A) at positions 37, 55, and 58, respectively. As methylation of the ribose at position 34 is influenced by the intracellular selenium status and the presence of this methyl group dramatically alters tertiary structure, we investigated the effect of the modifications at other positions as well as tertiary structure on its formation. Mutations were introduced within a synthetic gene encoded in an expression vector, transcripts generated and microinjected into Xenopus oocytes, and the resulting tRNA products analyzed for the presence of modified bases. The results suggest that efficient methylation of mcmU to yield mcmUm requires the prior formation of each modified base and an intact tertiary structure, whereas formation of modified bases at other positions, including mcmU, is not as stringently connected to precise primary and tertiary structure. These results, along with the observations that methylation of mcmU is enhanced in the presence of selenium and that this methyl group affects tertiary structure, further suggest that the mcmUm isoacceptor must have a role in selenoprotein synthesis different from that of the mcmU isoacceptor.

Keywords

1-methyladenine2′-O-ribose methylation5-methylcarboxymethyluridine5-methylcarboxymethyluridine-2′-O-methylriboseN6-isopentenyladenosinepseudouridineselenocysteinetRNA modification
Type
Research Article
Information
RNA , Volume 6 , Issue 9 , September 2000 , pp. 1306 - 1315
Copyright
2000 RNA Society

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