Cloning and characterization of two genes restoring acid phosphatase activity in pho1- mutants of Schizosaccharomyces pombe.

Schizosaccharomyces pombe acid phosphatase (APh) is a secreted cell surface glycoprotein which is deficient in pho1 mutants. By screening an S. pombe gene bank for sequences which can functionally rescue the pho1-44 mutation, we have isolated two genomic clones carried in plasmids pSp4B and pSp4C/2. These two sequences map of different genetic loci and show no cross hybridization by Southern blotting. pSp4C/2 was found to contain the PHO1 gene, and cells transformed with this plasmid produce a protein which cross-reacts with antibodies raised against the protein moiety of APh. Data from Northern blotting experiments show that pSp4C/2 encodes a 1.6-kb transcript, and that mRNA levels are increased when cells are grown in low concentrations of inorganic phosphate. The results indicate that pSp4C/2 contains the structural gene for APh, PHO1, whereas pSp4B appears to carry a gene coding for a minor species of APh, PHO4 which is not regulated by extracellular phosphate.