The Saccharomyces cerevisiae Isw2p-Itc1p complex represses INO1 expression and maintains cell morphology.
In the yeast Saccharomyces cerevisiae, IRE1 encodes a bifunctional protein with transmembrane kinase and endoribonuclease activities. HAC1 encodes a transcription factor which has a basic leucine zipper domain. Both gene products play a crucial role in the unfolded protein response. Mutants in which one of these genes is defective also ... show the inositol-auxotrophic (Ino(-)) phenotype, but the reason for this has not been clear. To investigate the mechanism underlying the Ino(-) phenotype, we screened a multicopy suppressor gene which can suppress the Ino(-) phenotype of the Delta hac1 strain. We obtained a truncated form of the ITC1 gene that has a defect in its 3' region. Although the truncated form of ITC1 clearly suppressed the Ino(-) phenotype of the Delta hac1 strain, the full-length ITC1 had a moderate effect. The gene products of ITC1 and ISW2 are known to constitute a chromatin-remodeling complex (T. Tsukiyama, J. Palmer, C. C. Landel, J. Shiloach, and C. Wu, Genes Dev. 13:686--697, 1999). Surprisingly, the deletion of either ITC1 or ISW2 in the Delta hac1 strain circumvented the inositol requirement and caused derepression of INO1 even under repression conditions, i.e., in inositol-containing medium. These data indicate that the Isw2p-Itc1p complex usually represses INO1 expression and that overexpression of the truncated form of ITC1 functions in a dominant negative manner in INO1 repression. It is conceivable that the repressor function of this complex is regulated by the C-terminal region of Itc1p.
Mesh Terms:
Adenosine Triphosphatases, Basic-Leucine Zipper Transcription Factors, Cloning, Molecular, Fungal Proteins, Genes, Suppressor, Inositol, Membrane Glycoproteins, Myo-Inositol-1-Phosphate Synthase, Phenotype, Plasmids, Protein Folding, Protein-Serine-Threonine Kinases, Repressor Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transcription Factors
Adenosine Triphosphatases, Basic-Leucine Zipper Transcription Factors, Cloning, Molecular, Fungal Proteins, Genes, Suppressor, Inositol, Membrane Glycoproteins, Myo-Inositol-1-Phosphate Synthase, Phenotype, Plasmids, Protein Folding, Protein-Serine-Threonine Kinases, Repressor Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transcription Factors
J. Bacteriol.
Date: Sep. 01, 2001
PubMed ID: 11489850
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