The essential Gcd10p-Gcd14p nuclear complex is required for 1-methyladenosine modification and maturation of initiator methionyl-tRNA.
Gcd10p and Gcd14p are essential proteins required for the initiation of protein synthesis and translational repression of GCN4 mRNA. The phenotypes of gcd10 mutants were suppressed by high-copy-number IMT genes, encoding initiator methionyl tRNA (tRNAiMet), or LHP1, encoding the yeast homolog of the human La autoantigen. The gcd10-504 mutation led to a reduction in steady-state levels of mature tRNAiMet, attributable to increased turnover rather than decreased synthesis of pre-tRNAiMet. Remarkably, the lethality of a GCD10 deletion was suppressed by high-copy-number IMT4, indicating that its role in expression of mature tRNAiMet is the essential function of Gcd10p. A gcd14-2 mutant also showed reduced amounts of mature tRNAiMet, but in addition, displayed a defect in pre-tRNAiMet processing. Gcd10p and Gcd14p were found to be subunits of a protein complex with prominent nuclear localization, suggesting a direct role in tRNAiMet maturation. The chromatographic behavior of elongator and initiator tRNAMet on a RPC-5 column indicated that both species are altered structurally in gcd10Delta cells, and analysis of base modifications revealed that 1-methyladenosine (m1A) is undetectable in gcd10Delta tRNA. Interestingly, gcd10 and gcd14 mutations had no effect on processing or accumulation of elongator tRNAMet, which also contains m1A at position 58, suggesting a unique requirement for this base modification in initiator maturation.
Anderson
J
J
Laboratory of Eukaryotic Gene Regulation, National Institute of Child Health and Human Development, Bethesda, Maryland 20892 USA.
Phan
L
L
Cuesta
R
R
Carlson
B A
BA
Pak
M
M
Asano
K
K
Björk
G R
GR
Tamame
M
M
Hinnebusch
A G
AG
D000241:Adenosine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D005800:Genes, Fungal; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010442:Peptide Chain Initiation, Translational; D012323:RNA Processing, Post-Transcriptional; D012358:RNA, Transfer, Met / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000254:growth & development; D013489:Suppression, Genetic
D009687:Nuclear Proteins; D012358:RNA, Transfer, Met; C089238:fMet-tRNA(fMet); C002230:1-methyladenosine; D000241:Adenosine