Structure and function of the yeast tRNA ligase gene

Area of Science:

• Molecular Biology
• Yeast Genetics

Background:

• Transfer RNA (tRNA) splicing is a crucial post-transcriptional modification process in eukaryotes.
• Yeast tRNA splicing requires two enzymes, including tRNA ligase, which is believed to be a single polypeptide with multiple catalytic activities.

Purpose of the Study:

• To determine the complete DNA sequence of the coding region for the Saccharomyces cerevisiae tRNA ligase gene.
• To characterize the protein properties and identify potential regulatory elements associated with the gene.

Main Methods:

• DNA sequencing of the entire coding region of the yeast tRNA ligase gene.
• Bioinformatic analysis to infer amino acid sequence, molecular weight, and protein properties.
• Identification and analysis of open reading frames (ORFs) within the sequenced region.

Main Results:

• The complete coding sequence of the Saccharomyces cerevisiae tRNA ligase gene was determined.
• The tRNA ligase is a basic protein comprising 827 amino acids, with an estimated molecular weight of 95,400 Da.
• The inferred amino acid sequence shows no significant homology to other known proteins with similar enzymatic activity.
• Two additional open reading frames, ORF1 and ORF2, were identified near the 5'-end of the ligase gene.
• ORF2 produces a divergent transcript initiating upstream of the tRNA ligase transcript and is co-regulated.

Conclusions:

• The characterization of the yeast tRNA ligase gene provides fundamental insights into the molecular machinery of tRNA splicing.
• The lack of homology suggests a unique evolutionary path for this essential yeast enzyme.
• The identification of upstream ORFs suggests complex transcriptional regulation of tRNA ligase expression in Saccharomyces cerevisiae.