A functional analysis of the repeated methionine initiator tRNA genes (IMT) in yeast
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Standard laboratory yeast strains have from four to five genes encoding the methionine initiator tRNA (IMT). Strain S288C has four IMT genes with identical coding sequences that are colinear with the RNA sequence of tRNAIMet. Each of the four IMT genes from strain S288C is located on a different chromosome. A fifth IMT gene with the same coding sequence is present in strain A364A but not in S288C. By making combinations of null alleles in strain S288C, we show that each of the four IMT genes is functional and that tRNAIMetis not limiting in yeast strains with three or more intact genes. Strains containing a single IMT2, 3 or 4 gene grow only after amplification of the remaining IMT gene. Strains with only the IMT1 gene intact are viable but grow extremely slowly; normal growth is restored by the addition of another IMT gene by transformation, providing a direct test for IMT function.
Key wordsMethionine Initiator tRNA tRNA(met) Yeast Multigene family
- IMT and imt
(imt=initiator methionine tRNA), designate the genotype of the wild-type and the mutant alleles respectively, of the initiator methionine transfer RNA gene
methionylated initiator methionine transfer RNA
eukaryotic initiation factor two
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