The Fission Yeast GATA Factor, Gaf1, Modulates Sexual Development via Direct Down-Regulation of ste11+ Expression in Response to Nitrogen Starvation

Gaf1 is the first GATA family zinc-finger transcription factor identified in Schizosaccharomyces pombe . Here, we report that Gaf1 functions as a negatively acting transcription factor of ste11 + , delaying the entrance of cells exposed to transient nitrogen starvation into the meiotic cycle. gaf1Δ strains exhibited accelerated G 1 -arrest upon nitrogen starvation. Moreover, gaf1Δ mutation caused increased mating and sporulation frequency under both nitrogen-starved and unstarved conditions, while overexpression of gaf1 + led to a significant impairment of sporulation. By microarray analysis, we found that approximately 63% (116 genes) of the 183 genes up-regulated in unstarved gaf1Δ cells were nitrogen starvation-responsive genes, and furthermore that 25 genes among the genes up-regulated by gaf1 Δ mutation are Ste11 targets ( e.g. , gpa1 + , ste4 + , spk1 + , ste11 + , and mei2 + ). The phenotype caused by gaf1Δ mutation was masked by ste11Δ mutation, indicating that ste11 + is epistatic to gaf1 + with respect to sporulation efficiency, and accordingly that gaf1 + functions upstream of ste11 + in the signaling pathway governing sexual development. gaf1Δ strains showed accelerated ste11 + expression under nitrogen starvation and increased ste11 + expression even under normal conditions. Electrophoretic mobility shift assay analysis demonstrated that Gaf1 specifically binds to the canonical GATA motif (5′-HGATAR-3′) spanning from −371 to −366 in ste11 + promoter. Consequently, Gaf1 provides the prime example for negative regulation of ste11 + transcription through direct binding to a cis -acting motif of its promoter.