Showing papers by "Jeffrey G. Williams published in 2006"
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TL;DR: Recent advances in understanding the signalling pathways that generate prestalk‐cell heterogeneity are described, focusing on the roles of the prestalk-cell inducer differentiation‐inducing factor‐1 (DIF‐1), the tip inducer cAMP and the transcription factors that mediate their actions.
Abstract: On starvation, Dictyostelium cells form a terminally differentiated structure, known as the fruiting body, which comprises stalk and spore cells Their precursors–prestalk and prespore cells–are spatially separated and accessible in a migratory structure known as the slug This simplicity and manipulability has made Dictyostelium attractive to both experimental and theoretical developmental biologists However, this outward simplicity conceals a surprising degree of developmental sophistication Multiple prestalk subtypes are formed and undertake a co-ordinated series of morphogenetic cell movements to generate the fruiting body This review describes recent advances in understanding the signalling pathways that generate prestalk-cell heterogeneity, focusing on the roles of the prestalk-cell inducer differentiation-inducing factor-1 (DIF-1), the tip inducer cAMP and the transcription factors that mediate their actions; these include signal transducer and activator of transcription (STAT) proteins, basic leucine zipper (bZIP) proteins and a Myb protein of a class previously described only in plants
111 citations
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TL;DR: DimB regulates DimB activity to generate a gradient of ecmA expression in the prestalk zone of the slug, and ChIP analysis shows that, in the presence of extracellular cAMP, DIF-1 causes DimB to associate with the ecmA promoter in vivo.
Abstract: 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.
58 citations
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TL;DR: MybE is necessary for DIF-1 responsiveness and for the correct differentiation of pstO cells and ALCs and the 22-nucleotide region was used to purify MybE, a protein with a single MYB DNA-binding domain of a type previously found only in a large family of plant transcription factors.
Abstract: PstA and pstO cells are the two major populations in the prestalk region of
the Dictyostelium slug and DIF-1 is a low molecular weight signalling
molecule that selectively induces pstO cell-specific gene expression. The two
cell types are defined by their differential use of spatially separated
regions of the ecmA promoter. Additionally, there are anterior-like
cells (ALCs) scattered throughout the rear, prespore region of the slug. They,
like the pstO cells, use a cap-site distal ecmA promoter segment
termed the ecmO region. When multimerised, a 22-nucleotide subsegment of the
ecmO region directs expression in pstA cells, pstO cells and ALCs. It also
directs DIF-inducible gene expression. The 22-nucleotide region was used to
purify MybE, a protein with a single MYB DNA-binding domain of a type
previously found only in a large family of plant transcription factors. Slugs
of a mybE-null (mybE–) strain express an ecmAO:lacZ
fusion gene (i.e. a reporter construct containing the ecmA and ecmO promoter
regions) in pstA cells but there is little or no expression in pstO cells and
ALCs. The ecmA gene is not induced by DIF-1 in a mybE-strain. Thus,
MybE is necessary for DIF-1 responsiveness and for the correct differentiation
of pstO cells and ALCs.
49 citations