IUBMB Enzyme Nomenclature


Accepted name: multisite-specific tRNA:(cytosine-C5)-methyltransferase

Reaction: (1) S-adenosyl-L-methionine + cytosine34 in tRNA precursor = S-adenosyl-L-homocysteine + 5-methylcytosine34 in tRNA precursor
(2) S-adenosyl-L-methionine + cytosine40 in tRNA precursor = S-adenosyl-L-homocysteine + 5-methylcytosine40 in tRNA precursor
(3) S-adenosyl-L-methionine + cytosine48 in tRNA = S-adenosyl-L-homocysteine + 5-methylcytosine48 in tRNA
(4) S-adenosyl-L-methionine + cytosine49 in tRNA = S-adenosyl-L-homocysteine + 5-methylcytosine49 in tRNA

Other name(s): multisite-specific tRNA:m5C-methyltransferase; TRM4 (gene name, gene corresponding to ORF YBL024w)

Systematic name: S-adenosyl-L-methionine:tRNA (cytosine-C5)-methyltransferase

Comments: The enzyme from Saccharomyces cerevisiae is responsible for complete 5-methylcytosine methylations of yeast tRNA. The incidence of modification depends on the cytosine position in tRNA. At positions 34 and 40, 5-methylcytosine is found only in two yeast tRNAs (tRNALeu(CUA) and tRNAPhe(GAA), respectively), whereas most other elongator yeast tRNAs bear either 5-methylcytosine48 or 5-methylcytosine49, but never both in the same tRNA molecule [1]. The formation of 5-methylcytosine34 and 5-methylcytosine40 is a strictly intron-dependent process, whereas the formation of 5-methylcytosine48 and 5-methylcytosine49 is an intron-independent process [2,3].

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Motorin, Y. and Grosjean, H. Multisite-specific tRNA:m5C-methyltransferase (Trm4) in yeast Saccharomyces cerevisiae: identification of the gene and substrate specificity of the enzyme. RNA 5 (1999) 1105-1118. [PMID: 10445884]

2. Jiang, H.Q., Motorin, Y., Jin, Y.X. and Grosjean, H. Pleiotropic effects of intron removal on base modification pattern of yeast tRNAPhe: an in vitro study. Nucleic Acids Res. 25 (1997) 2694-2701. [PMID: 9207014]

3. Strobel, M.C. and Abelson, J. Effect of intron mutations on processing and function of Saccharomyces cerevisiae SUP53 tRNA in vitro and in vivo. Mol. Cell Biol. 6 (1986) 2663-2673. [PMID: 3537724]

4. Walbott, H., Husson, C., Auxilien, S. and Golinelli-Pimpaneau, B. Cysteine of sequence motif VI is essential for nucleophilic catalysis by yeast tRNA m5C methyltransferase. RNA 13 (2007) 967-973. [PMID: 17475914]

[EC created 1976 as EC, part transferred 2011 to EC]

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