Myb‐binding site regulates the expression of glucosamine‐6‐phosphate isomerase in Dictyostelium discoideum

A homolog of the glucosamine-6-phosphate isomerase in the cellular slime mold Dictyostelium discoideum has been analyzed. The gene disruption mutant was arrested at the mound stage, demonstrating that the gene is important for development. The gene was expressed in vegetatively growing cells, silenced on starvation and expressed again in prestalk cells during the multicellular stages. The upstream region of the gene (1376 bp relative to ATG) was cloned and sequenced to study the transcription control mechanisms. Analysis of deletion mutants and a site-directed mutant indicated that the Myb-binding sequence (5′-AACTG-3′) localized in the upstream region is important for gene expression. The results of gel-shift assays showed the presence of an Myb-related protein binding to the sequence at the growing phase and another protein binding to the sequence at developmental stages.