The Dictyostelium bZIP transcription factor DimB regulates prestalk-specific gene expression.
The ecmA gene is specifically expressed in prestalk cells and its transcription is induced by the chlorinated hexaphenone DIF-1. We have purified a novel bZIP transcription factor, DimB, by affinity chromatography on two spatially separated ecmA promoter fragments. Mutagenesis of the cap-site proximal DimB-binding site (the -510 site) greatly decreases ecmA expression in the pstO cells, which comprise the rear half of the prestalk zone, and also in the Anterior-Like Cells, which lie scattered throughout the prespore region. However, DimB is not essential for normal expression of the ecmA gene, instead it spatially limits its expression; ecmA is relatively highly expressed in the subset of prestalk cells that coats the prestalk zone, but in slugs of a DimB-null strain, ecmA is highly expressed throughout the prestalk zone. Because the -510 site is required for correct ecmA expression, we posit a separate activator protein that competes with DimB for binding to the -510 site. DimB rapidly accumulates in the nucleus when cells are exposed to DIF-1, and ChIP analysis shows that, in the presence of extracellular cAMP, DIF-1 causes DimB to associate with the ecmA promoter in vivo. Thus, DIF-1 regulates DimB activity to generate a gradient of ecmA expression in the prestalk zone of the slug.
Zhukovskaya
Natasha V
NV
School of Life Sciences, University of Dundee, MSI/WTB Complex, UK.
Fukuzawa
Masashi
M
Yamada
Yoko
Y
Araki
Tsuyoshi
T
Williams
Jeffrey G
JG
D000595:Amino Acid Sequence; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004023:Dictyostelium / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006588:Hexanones / Q000378:metabolism; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000502:physiology; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
D050976:Basic-Leucine Zipper Transcription Factors; D016326:Extracellular Matrix Proteins; D006588:Hexanones; D015800:Protozoan Proteins; C053433:1-((3,5-dichloro)-2,6-dihydroxy-4-methoxyphenyl)-1-hexanone; D000242:Cyclic AMP