Nucleocytoplasmic shuttling of a GATA transcription factor functions as a development timer

Biological oscillations are observed at many levels of cellular organization. In the social amoebae Dictyostelium discoideum, starvation-triggered multicellular development is organized by periodic cAMP waves, which provide both chemoattractant gradients and developmental signals. We report that GtaC, a GATA transcription factor, exhibits rapid nucleocytoplasmic shuttling in response to cAMP waves. This behavior requires coordinated action of a nuclear localization signal and reversible G protein-coupled receptor (GPCR)-mediated phosphorylation. While both are required for developmental gene expression, receptor occupancy promotes nuclear exit of GtaC, which leads to a transient burst of transcription at each cAMP cycle. We demonstrate that this biological circuit, like an “edge trigger”, filters out high frequency signals and counts those admitted, thereby enabling cells to modulate gene expression according to the dynamic pattern of the external stimuli. Transcriptional profiling during early development of wild-type, gtaC, GFP-GtaC/gtaC, and NLSex-GFP-GtaC/gtaC strains