Cloning and manipulation of the Schizosaccharomyces pombe his7 +gene as a new selectable marker for molecular genetic studies

We have cloned the his7⁺ gene of the fission yeast Schizosaccharomyces pombe by complementation of the recessive mutant allele his7-366. The his7⁺ gene is able to complement a mutation of the Escherichia coli hisI gene, suggesting that his7⁺ encodes a phosphoribosyl-AMP cyclohydrase. Subcloning experiments localize the gene to a 1.9-kb XbaI-BglII fragment. We describe the construction of plasmids to facilitate the use of his7⁺ as a selectable marker in S. pombe studies. Plasmid pEA2 carries his7⁺ cloned into the pUC18 polylinker. From either pEA2 or the original his7⁺ clone, pMN1, fragments carrying his7⁺ can be isolated using a variety of restriction enzymes for the construction of gene disruptions. Plasmid pEA500 is a cloning vector that carries his7⁺ and ars1, yet retains the ability to use the blue/white color screen to identify recombinants.