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A protein with similarity to the human retinoblastoma binding protein 2 acts specifically as a repressor for genes regulated by the b mating type locus in Ustilago maydis
Author(s) -
QuadbeckSeeger Claudia,
Wanner Gerhard,
Huber Sieglinde,
Kahmann Regine,
Kämper Jörg
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.02128.x
Subject(s) - biology , ustilago , repressor , genetics , locus (genetics) , gene , mating type , transcription factor
Pathogenic development in the corn smut fungus Ustilago maydis is controlled by a heterodimer of the two homeodomain proteins bE and bW which are encoded by the b mating type locus. The bE/bW heterodimer is thought to achieve its function as a transcriptional regulator of pathogenicity genes, either directly by binding to cis regulatory sequences or indirectly via a b ‐dependent regulatory cascade. In a screen for components of the b ‐dependent regulatory cascade we have isolated Rum1 ( r egulator U . m aydis 1), a protein with similarities to the human retinoblastoma binding protein 2. Deletion of rum1 results in expression of several b regulated genes independently from their activation via the bE/bW heterodimer. rum1 mutant strains remain pathogenic, proliferate in planta, but fail to produce spores. The defect leads to an arrest in spore development at a defined stage before the spore wall is generated. Deduced from the highly conserved domain structure of Rum1 that includes a DNA‐binding motif and a region known to facilitate the interaction with histone deacetylases, we propose that Rum1 functions as a transcriptional repressor through the modulation of chromatin structure.