Mapping of the Cryptococcus neoformans MAT α Locus: Presence of Mating Type-Specific Mitogen-Activated Protein Kinase Cascade Homologs

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Abstract
In this study we investigated the relationship between the MAT α locus of Cryptococcus neoformans and several MAT α-specific mitogen-activated protein (MAP) kinase signal transduction cascade genes, including STE12 α, STE11 α, and STE20 α. To resolve the location of the genes, we screened a cosmid library of the MAT α strain B-4500 (JEC21), which was chosen for the C. neoformans genome project. We isolated several overlapping cosmids spanning a region of about 71 kb covering the entire MAT α locus. It was found that STE12 α, STE11 α, and STE20 α are imbedded within the locus rather than closely linked to the locus. Furthermore, three copies of MF α, the mating type α-pheromone gene, a MAT α-specific myosin gene, and a pheromone receptor ( CPR α) were identified within the locus. We created a physical map, based on the restriction enzyme Bam HI, and identified both borders of the MAT α locus. The MAT α locus of C. neoformans is approximately 50 kb in size and is one of the largest mating type loci reported among fungi with a one-locus, two-allele mating system.