Isolation and Characterization of an Invertase and Its Repressor Genes fromSchizosaccharomyces pombe

Abstract

PCR was used to isolate an invertase homolog gene from the fission yeastSchizosaccharomyces pombe.The clonedinv1+gene encodes a protein of 581 amino acids with 16 potential asparagine-linked glycosylation sites, and has 39% and 38% identity to theSchwanniomyces occidentalisandSaccharomyces cerevisiae SUC2invertases. When theinv1+gene was disrupted,S. pombestrains lacked detectable invertase activity. This result showed that theinv1+gene encodes only one active invertase inS. pombecells. The transcription ofinv1+is repressed in the presence of glucose. The transcription ofinv1+was not affected incyr1Δ strain which lacks adenylate cyclase activity, unlike transcription ofS. pombe fbp1+gene. We have identified anS. pombegene (scr1+) that encodes a homolog of theAspergillus nidulansCREA which is required for glucose repression of the glyconeogenic pathway. Although the deletion ofscr1+did not influence the transcription offbp1+gene, glucose repression of theinv1+gene was severely affected. These results showed that glucose repression ofinv1+gene is dependent onscr1+gene, andS. pombecAMP signalling pathway may not be essential for glucose repression ofinv1+gene.