Nucleotide sequence of ORF2: an open reading frame upstream of the tRNA ligase gene

During the course of sequencing the tRNA ligase gene from the yeast Saccharomyces cerevisiae , an open reading frame, ORF2, was discovered in its vicinity (1). ORF2 was found to be the locus of a single copy, essential gene (S. Westaway and J. Abelson, unpublished observations) with a transcript starting only 125 nucleotides upstream of tRNA ligase (1). The proximity of ORF2 to tRNA ligase suggested that their products might be transcriptionally coregulated and that its product might participate in the processing of tRNA precursors. For this reason we completely sequenced both strands of the ORF2 DNA using the method of Sanger, et. al. (2) .The sequence is shown below, with the corresponding amino acid sequence of the putative protein product of 623 amino acids (mw 71,300). The left arrows show the transcription starts of tRNA ligase, and the right arrows show the initiation sites of ORF2 transcription. The protein is not significantly homologous to any protein on the NBRF database, leaving its function in question.