Consistent with the observation that lack of modification at the 2 and 5 positions causes very different clinical symptoms (liver failure (TRMU) or hypertrophic cardiomyopathy (GTPBP3 and MTO1) respectively), we have demonstrated that the phenotype of the mutant lacking the modification at position 2 (mttu-1) of U34 is appreciably different from that of mutants lacking the modification at position 5 (mtcu-1 or mtcu-2). Here, MTO1 is linked to Hepatic failure.