Trm7p catalyses the formation of two 2′‐ O ‐methylriboses in yeast tRNA anticodon loop

The genome of Saccharomyces cerevisiae encodes three close homologues of the Escherichia coli 2′‐ O ‐rRNA methyltransferase FtsJ/RrmJ, designated Trm7p, Spb1p and Mrm2p. We present evidence that Trm7p methylates the 2′‐ O ‐ribose of nucleotides at positions 32 and 34 of the tRNA anticodon loop, both in vivo and in vitro . In a trm7 Δ strain, which is viable but grows slowly, translation is impaired, thus indicating that these tRNA modifications could be important for translation efficiency. We discuss the emergence of a family of three 2′‐ O ‐RNA methyltransferases in Eukaryota and one in Prokaryota from a common ancestor. We propose that each eukaryotic enzyme is located in a different cell compartment, in which it would methylate a different RNA that can adopt a very similar secondary structure.