title: 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.
abstract: 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 (regulator U. maydis 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.
authors.affiliation: Institut für Genetik und Mikrobiologie, Ludwig-Maximilians-Universität München, Maria-Ward-Strasse 1a, D-80638 München, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Quadbeck-Seeger
authors.forename: G
authors.initials: G
authors.lastname: Wanner
authors.forename: S
authors.initials: S
authors.lastname: Huber
authors.forename: R
authors.initials: R
authors.lastname: Kahmann
authors.forename: J
authors.initials: J
authors.lastname: Kämper
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D006801:Humans; D000072235:Mating Factor; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics*; D010641:Phenotype; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid; D014588:Ustilago / Q000235:genetics*
chemical_list: D017931:DNA Primers; D005656:Fungal Proteins; D010455:Peptides; D012097:Repressor Proteins; C086077:Rum1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D000072235:Mating Factor