Isolation of the fructose-1,6-bisphosphatase gene of the yeast Schizosaccharomyces pombe. Evidence for transcriptional regulation.

The fructose-1,6-bisphosphatase structural gene (FBP+) of Schizosaccharomyces pombe has been isolated by genetic complementation of a deficient mutant, which is characterized by the inability to grow on a nonfermentable carbon source such as glycerol. Growth on glycerol-containing medium was restored in a S. pombe fructose-1,6-bisphosphatase-deficient mutant (fbp-16) when it was transformed with a plasmid (pAVO4) carrying FBP+. The transformant displayed a 5-fold increase in enzymatic activity when compared to the parental S. pombe strain. Subcloning of DNA fragments from the 8.5-kilobase (kb) insert of pAVO4 defined a 4-kb DNA fragment which contained the functional FBP+ gene and its regulatory region. When this gene was placed under the control of the lac promoter-operator, functional expression in Escherichia coli was obtained, as deduced by complementation of bacterial fructose-1,6-bisphosphatase mutants. The FBP+ gene encodes a 1.9-kb glucose-repressible transcript whose appearance in S. pombe is correlated with fructose-1,6-bisphosphatase derepression in glycerol-containing medium. We suggest that the regulation of the S. pombe FBP+ gene is exerted at the transcriptional level. The S. pombe FBP+ gene gave rise to a 1.9-kb transcript in Saccharomyces cerevisiae, but not to measurable enzymatic activity.