Mutations at the yeast SUP4 tRNATyr locus: DNA sequence changes in mutants lacking suppressor activity

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The SUP4 gene encodes a tyrosine transfer RNA (tRNA) crucial for protein synthesis.
• Mutations in tRNA genes can affect gene expression and cellular function.
• Understanding mutation patterns provides insights into gene structure and function.

Purpose of the Study:

• To characterize mutations within the yeast SUP4 tyrosine tRNA gene.
• To correlate genetic mapping data with DNA sequence alterations.
• To investigate the distribution and nature of mutations in the tRNA gene, including its intervening sequence.

Main Methods:

• Selection of yeast strains with inactivating mutations in the SUP4 gene.
• Meiotic genetic fine structure mapping of 69 SUP4 mutants.
• Cloning and DNA sequencing of SUP4 genes from 32 mutant strains using the dideoxynucleotide terminator method.
• Analysis of mutation positions relative to the tRNA gene structure.

Main Results:

• Three-fourths of SUP4 mutations were point alterations, with the remainder resembling deletions.
• Genetic mapping and DNA sequencing showed good colinearity of mutation positions.
• One mutation site was identified within the intervening sequence, characterized by AT to TA transitions.
• Mutations were generally distributed throughout the tRNA coding sequence, with none found in flanking regions or the 3' side of the intervening sequence.

Conclusions:

• The study successfully mapped and sequenced SUP4 gene mutations, revealing their distribution and types.
• The findings highlight the correlation between genetic and sequence data for mutations within a tRNA gene.
• The identification of a mutation in the intervening sequence provides specific information about functional regions of the tRNA gene.