Schizosaccharomyces pombe pcr1+ Encodes a CREB/ATF Protein Involved in Regulation of Gene Expression for Sexual Development

Abstract

The Schizosaccharomyces pombe pcr1 gene encodes a bZIP protein that apparently belongs to the cyclic AMP response element (CRE)-binding protein/activating transcription factor family. The deduced pcr1 gene product consists of 171 amino acid residues and is most similar to the mammalian CRE-BP1. A glutathione S-transferase-Pcr1 fusion protein produced in Escherichia coli was able to bind specifically to the CRE motif in vitro. Analysis with anti-Pcr1 serum suggested that Pcr1 is included in the major CRE-binding factors present in the S. pombe cell extract. Disruption of the pcr1 gene was not lethal, but the disruptant showed cold-sensitive growth on rich medium. The disruptant was also inefficient in mating and sporulation, though it was not completely sterile. Expression of the ste11 gene, which encodes a key transcription factor for sexual development, was greatly reduced in the disruptant, and overexpression of ste11+ suppressed the deficiency of the pcr1 disruptant in sexual development. It has been shown that expression of ste11 is negatively regulated by cyclic AMP-dependent protein kinase (PKA) and that the loss of PKA activity results in ectopic sexual development. Disruption of pcr1 blocked ectopic sexual development. Furthermore, disruption of pcr1 reduced expression of fbp1, a glucose-repressible gene negatively regulated by PKA. These results suggest that Pcr1 is a putative transcriptional regulator whose activity may be controlled by PKA. Alternatively, its activity may be independent of PKA, and full induction of ste11 and fbp1 expression requires the function of Pcr1 in addition to elimination of the repression by PKA.