Evidence that a combined activator-repressor protein regulates Dictyostelium stalk cell differentiation.

Abstract

The ecmA gene is expressed in Dictyostelium prestalk cells and is inducible by differentiation‐inducing factor (DIF), a low‐molecular‐weight lipophilic substance. The ecmB gene is expressed in stalk cells and is under negative control by two repressor elements. Each repressor element contains two copies of the sequence TTGA in an inverted relative orientation. There are activator elements in the ecmA promoter that also contain two TTGA sequences, but in the same relative orientation. Gel retardation assays suggest that the same protein binds to the ecmB repressor and the ecmA activator. We propose that DIF induces prestalk cell differentiation by activating this protein and that the protein also binds to the promoters of stalk‐specific genes, acting as a repressor that holds cells in the prestalk state until culmination is triggered.

A bZIP/bRLZ transcription factor required for DIF signaling inDictyostelium

“…A minimal DIF-response element has been described that is both necessary and sufficient for DIFinduced gene expression in cell culture (Kawata et al, 1996). Furthermore, several activities have been identified in cell extracts that bind to this element in vitro and, ultimately, led to the identification of the Dictyostelium STAT family of transcription factors (Fukuzawa et al, 2001;Kawata et al, 1997).…”

Regulation ofDictyosteliumprestalk-specific gene expression by a SHAQKY family MYB transcription factor

“…Nuclear extracts were prepared from slug stage cells and gel retardation assays performed as previously (Kawata et al, 1996). The probe was made by annealing complementary oligonucleotides with BamHI cohesive ends, derived from the 30-mer sequence ( Fig.…”

“…The smallest ecmO promoter sub-fragment known to direct pstOspecific gene expression is 132 nucleotides in length (Kawata et al, 1996). We first showed that a 94-mer, centred within the 132-mer, also directs pstO-specific gene expression when fused to heterologous basal promoter elements (Fig.…”

“…Previous mutational analyses of the ecmA promoter identified a 132-nucleotide subsegment ( Fig. 1) that directs pstO-specific gene expression (Early et al, 1993;Kawata et al, 1996). When a G-box, a non-cell-typespecific promoter element (reviewed by Schnitzler et al, 1994), was fused to the multimerised form of a distal sub-region of the 132-mer expression was weakly DIF-inducible.…”

The Role of Tyrosine Phosphorylation in Regulation of Signal Transduction Pathways in Unicellular Eukaryotes

“…The regulatory Dd-STATa action on processes of D. discoideum cell differentiation is realized through activation of transcription of genes ecmA and ecmB responsible for prestalk cell differentiation. It has been established that Dd-STATa can binds to both the ecmA activator and ecmB repressor elements in promoters of these genes, as both types of the regulators contain repeats of TTGA sequences, which are recognized by Dd-STATa (Kawata, 1996;Ceccarelli et al, 2000). Besides, Dd-STATa has recently been shown to act as a transcriptional activator of the gene cudA, whose expression is essential for correction of terminal differentiation of D. discoideum (Fukuzawa and Williams, 2000).…”