Schizosaccharomyces pombe ste11 encodes a high-mobility group family transcriptional activator that is pivotal in sexual development. Transcription of ste11 is induced by starvation of nutrients via a decrease of the cAMP-dependent protein kinase (PKA) activity. Here we report the identification of a novel transcription factor, Rst2p, that directly regulates ste11 expression. Cells in which the rst2 gene was disrupted expressed ste11 poorly and were sterile, and this sterility could be suppressed by artificial expression of ste11. Disruption of rst2 suppressed hypermating and hypersporulation in the PKA-null mutant, whereas overexpression of rst2 induced sexual development in the PKA-activated mutant. Cloning analysis indicated that Rst2p was a Cys(2)His(2) zinc-finger protein carrying 567 amino acid residues. Rst2p could bind specifically to a stress response element-like cis element located in the ste11 promoter region, which was important for ste11 expression. Meanwhile, transcription of ste11 was reduced significantly by a defective mutation in itself. An artificial supply of functional Ste11p circumvented this reduction. A complete Ste11p-binding motif (TR box) found in the promoter region was necessary for the full expression of ste11, suggesting that Ste11p is involved in the activation of ste11. We conclude that transcription of ste11 is under autoregulation in addition to control through the PKA-Rst2p pathway.