Sequence elements necessary for transcriptional activation of BAD1 in the yeast phase of Blastomyces dermatitidis.
Blastomyces dermatitidis is a dimorphic fungal pathogen that converts from mycelia or conidia to a host-adapted yeast morphotype upon infection. Conversion to the yeast form is accompanied by the production of the virulence factor BAD1. Yeast-phase-specific expression of BAD1 is transcriptionally regulated, and its promoter shares homology with that of the yeast-phase-specific gene YPS3 of Histoplasma capsulatum. Serial truncations of the BAD1 upstream region were fused to the lacZ reporter to define functional areas in the promoter. Examination of PBAD1-lacZ fusions in B. dermatitidis indicated that BAD1 transcription is upregulated in the yeast phase. The 63-nucleotide box A region conserved in the YPS3 upstream region was shown to be an essential component of the minimal BAD1 promoter. A matched PYPS3-lacZ construct indicated that this same region was needed for minimal YPS3 promoter activity in B. dermatitidis transformants. Reporter activity in H. capsulatum transformants similarly showed a requirement for box A in the minimal BAD1 promoter. Several putative transcription factor binding sites were identified within box A of BAD1. Replacement of two of these predicted sites within box A--a cAMP responsive element and a Myb binding site--sharply reduced transcriptional activity, indicating that these regions are critical in dictating the yeast-phase-specific expression of this crucial virulence determinant of B. dermatitidis.
Rooney
Peggy J
PJ
Department of Medical Microbiology and Immunology, University of Wisconsin Medical School, Madison, WI 53792, USA.
Klein
Bruce S
BS
D001758:Blastomyces / Q000235:genetics*; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D006023:Glycoproteins / Q000235:genetics*; D006658:Histoplasma / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D015533:Transcriptional Activation; D014774:Virulence / Q000235:genetics
D017931:DNA Primers; D005656:Fungal Proteins; D006023:Glycoproteins; C087923:Yps-3 protein, Ajellomyces capsulata; D000242:Cyclic AMP