A primordial tRNA modification required for the evolution of life?

The evolution of reading frame maintenance must have been an early event, a nd presumably preceded the emergence of the three domains Archaea, Bacteria and Eukarya, Features evolved early in reading frame maintenance may still exist in present-day organisms. We show that one such feature may be the m odified nucleoside 1-methylguanosine (m(1)G37), which prevents frameshiftin g and is present adjacent to and 3' of the anticodon (position 37) in the s ame subset of tRNAs from all organisms, including that with the smallest se quenced genome (Mycoplasma genitalium), and organelles. We have identified the genes encoding the enzyme tRNA(m(1)G37)methyltransferase from all three domains. We also show that they are orthologues, and suggest that they ori ginated from a primordial gene. Lack of m(1)G37 severely impairs the growth of a bacterium and a eukaryote to a similar degree. Yeast tRNA(m(1)G37)met hyltransferase also synthesizes 1-methylinosine and participates in the for mation of the Y-base (yW), Our results suggest that m(1)G37 existed in tRNA before the divergence of the three domains, and that a tRNA(m(1)G37)methyl transferase is part of the minimal set of gene products required for life.