Cell-type-dependent repression of yeast a-specific genes requires Itc1p, a subunit of the Isw2p-Itc1p chromatin remodelling complex.
In Saccharomyces cerevisiae MATa haploid cells, the a-specific genes are expressed, whereas in the MATalpha haploid and MATa/alpha diploid cell types their transcription is repressed. It is shown in this report that Itc1p, a component of the ATP-dependent Isw2p-Itc1p chromatin remodelling complex, is required for the repression of a-specific genes. It has previously been reported that disruption of the ITC1 gene leads, in MATalpha cells, to an aberrant cell morphology resembling the polarized mating projection of cells responding to pheromone. The activation of the pheromone signalling pathway in itc1 mutants of both mating types was examined and found to be constitutively active in MATalpha itc1 but not in MATa itc1 cells. Furthermore, unlike the wild-type, MATalpha itc1 and MATa/alpha itc1/itc1 cells secrete a-factor and express significant levels of other a-specific genes. The results indicate that the inappropriate a-factor production in a MATalpha context, due to the derepression of the a-specific genes, produces an autocrine signalling loop that leads to the aberrant morphology displayed by MATalpha itc1 cells. It is suggested that the Isw2p-Itc1p complex contributes to maintain the repressive chromatin structure described for the asg operator present in the promoters of a-specific genes.
Ruiz
Cristina
C
Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain.
Escribano
Victoria
V
Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, C/Arturo Duperier 4, 28029 Madrid, Spain.
Morgado
Eulalia
E
Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, C/Arturo Duperier 4, 28029 Madrid, Spain.
Molina
María
M
Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain.
Mazón
María J
MJ
Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, C/Arturo Duperier 4, 28029 Madrid, Spain.
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D004171:Diploidy; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006238:Haploidy; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010675:Pheromones / Q000494:pharmacology; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D002843:Chromatin; D018398:Homeodomain Proteins; C086468:ISWI protein; C096063:MATA1 protein, S cerevisiae; D010675:Pheromones; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases