Transcription of the triose-phosphate-isomerase gene of Schizosaccharomyces pombe initiates from a start point different from that in Saccharomyces cerevisiae.
Gene tpi, encoding the glycolytic enzyme triose phosphate isomerase (TPI) from the fission yeast Schizosaccharomyces pombe was cloned by complementation of a Saccharomyces cerevisiae tpil mutant. Nucleotide sequence analysis of the cloned gene revealed a single open reading frame (ORF) encoding a protein 59% homologous to S. cerevisiae TPI. The gene has a very high codon usage bias. Messenger RNA synthesis initiates at two points located 38 and 44 nucleotides downstream from a TATA box promoter sequence. In S. cerevisiae, transcription of this S. pombe gene initiates about 26 nucleotides downstream from the S. pombe start points. This observation indicates that the two yeasts have diverged in the mechanism which determines the 5' end of the messenger RNA relative to the TATA box. It appears that in some respects the transcription initiation mechanism of S. pombe more closely resembles that of higher eukaryotes than does the S. cerevisiae mechanism.
Russell PR