FURTHER ANALYSIS OF THE CAP59 LOCUS OF CRYPTOCOCCUS-NEOFORMANS - STRUCTURE DEFINED BY FORCED EXPRESSION AND DESCRIPTION OF A NEW RIBOSOMAL PROTEIN-ENCODING GENE

Cryptococcus neoformans (Cn) produces an extracellular polysaccharide capsule that is an essential factor for virulence. We previously isola ted a gene, CAP59, which is necessary for capsule formation. To dissec t the functional region of CAP59, we placed it under control of the Cn GAL7 promoter (pGAL7), Among the several pGAL7::CAP59 fusion construc ts, only the one containing the entire open reading frame of CAP59 was able to complement the acapsular phenotype under galactose induction. A missense mutation in the coding region abolished complementation by the fusion construct. We also found that the CAP59 locus is contiguou s to a convergently transcribed L27 ribosomal protein-encoding gene (C L27), The distance between the cDNA ends of these two genes is only 25 bp. CL27 has two introns near its N terminus. The translated CL27 pro tein is 183 amino acids (aa) in length with an estimated molecular mas s of 20 kDa, and the first 34 aa at the N terminus may be a targeting peptide for mitochondria. A high degree of restriction-fragment-length polymorphism was detected in the DNA sequence containing CAP59 and CL 27.