THE INTRON-CONTAINING HSP82 GENE OF THE DIMORPHIC PATHOGENIC FUNGUS HISTOPLASMA-CAPSULATUM IS PROPERLY SPLICED IN SEVERE HEAT-SHOCK CONDITIONS

We have isolated and characterized a heat-inducible gene, hsp82, from the dimorphic pathogenic fungus Histoplasma capsulatum, which is filamentous mold at 25-degrees-C and a unicellular yeast at 37-degrees-C. This gene, which has a high degree of homology with other members of the hsp82 gene family, is split into three exons and two introns of 122 and 86 nucleotides, respectively. Contrary to what has been demonstrated in Drosophila melanogaster, Saccharomyces, cerevisiae, and other organisms, hsp82 mRNA in H. capsulatum is properly spliced during the severe heat conditions of 37 to 40-degrees-C in the temperature-sensitive Downs strain. Splicing accuracy was also observed at 42-degrees-C in the temperature-tolerant G222B strain, which showed no evidence of accumulation of primary transcripts. Furthermore, the intron containing the beta-tubulin gene is also properly spliced at the upper temperature range, suggesting that the lack of a block in splicing may be a general phenomenon in this organism.