Expression of alpha- and beta-tubulin genes during dimorphic-phase transitions of Histoplasma capsulatum.
Recent investigations have confirmed the presence of one alpha-tubulin gene (TUB1) and one beta-tubulin gene (TUB2) in the dimorphic fungus Histoplasma capsulatum. In the present study, Northern blot (RNA blot) analyses revealed multiple alpha-tubulin transcripts and a single beta-tubulin transcript in the yeast and mycelial phases of the high-virulence 217B strain and low-virulence Downs strain. S1 nuclease protection assays demonstrated one initiation start site and two major stop sites for the TUB1 transcripts, suggesting that variations in 3' processing generate the alpha-tubulin messages of 2.5 and 2.0 kilobases. Dot blot hybridization experiments indicated that tubulin gene expression is developmentally regulated during the dimorphic phase transitions. alpha- and beta-tubulin mRNAs increased six- to eightfold during the yeast-to-mycelium conversion and decreased two- to threefold during the reverse transition. These changes in tubulin mRNA content coincided with major morphological events associated with H. capsulatum development. Western blots (immunoblots) of H. capsulatum yeast-specific proteins resolved by two-dimensional gel electrophoresis demonstrated a single alpha- and a single beta-tubulin isoform. Multiple tubulin polypeptides expressed in mycelia are probably products of posttranslational modifications.
Harris
G S
GS
Department of Biology, St. Louis University, Missouri 63103.
Keath
E J
EJ
Medoff
J
J
D004720:Endonucleases; D005786:Gene Expression Regulation; D005800:Genes, Fungal; D006658:Histoplasma / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014158:Transcription, Genetic; D014404:Tubulin / Q000235:genetics* / Q000378:metabolism
D014404:Tubulin; D004720:Endonucleases; D015719:Single-Strand Specific DNA and RNA Endonucleases