Analysis of the promoter of the cudA gene reveals novel mechanisms of Dictyostelium cell type differentiation.
The cudA gene encodes a nuclear protein that is essential for normal multicellular development. At the slug stage cudA is expressed in the prespore cells and in a sub-region of the prestalk zone. We show that cap site distal promoter sequences direct cudA expression in prespore cells, while proximal sequences direct expression in the prestalk sub-region. The promoter domain that directs prespore-specific transcription consists of a positively acting region, that has the potential to direct expression in all cells within the slug, and a negatively acting region that prevents expression in the prestalk cells. Dd-STATa is the STAT protein that regulates commitment to stalk cell gene expression, where it is known to function as a transcriptional repressor. We show that Dd-STATa binds in vitro to the positively acting part of the prespore domain of the cudA promoter. However, Dd-STATa cannot be utilised for this purpose in vivo, because analysis of a Dd-STATa null mutant strain shows that Dd-STATa is not necessary for cudA transcription in prespore cells. In contrast, the part of the cudA promoter that directs prestalk-specific expression contains a binding site for Dd-STATa that is essential for its biological activity. Dd-STATa appears therefore to serve as a direct activator of cudA transcription in prestalk cells, while a protein with a DNA binding specificity highly related to that of Dd-STATa is utilised to activate cudA transcription in prespore cells.
Fukuzawa
M
M
Department of Anatomy and Physiology, University of Dundee, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, UK.
Williams
J G
JG
D000199:Actins / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D003001:Cloning, Molecular; D004023:Dictyostelium / Q000166:cytology* / Q000235:genetics* / Q000502:physiology; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D015800:Protozoan Proteins / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000235:genetics; D017384:Sequence Deletion; D013170:Spores; D014158:Transcription, Genetic
D000199:Actins; C107317:CudA protein, Dictyostelium discoideum; D009687:Nuclear Proteins; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D012264:Ribonucleotide Reductases