CLONING OF CDNAS FROM ARABIDOPSIS-THALIANA THAT ENCODE PUTATIVE PROTEIN PHOSPHATASE 2C AND A HUMAN DR1-LIKE PROTEIN BY TRANSFORMATION OF A FISSION YEAST MUTANT

We characterized three Arabidopsis thaliana cDNA clones that could rescue the sterile phenotype of the Schizosaccharomyces pombe pde1 mutant, which is defective in cAMP phosphodiesterase. The first clone had a coding capacity of 399 amino acids that is 35% identical with rat protein phosphatase 2C (PP2C). The second had a coding capacity of 159 amino acids that is 41% identical with human Dr1. Dr1 has been shown to interact with TATA-binding protein (TBP) and block its ability to activate transcription. The third encoded Arabidopsis TBP itself. Saccharomyces cerevisiae TBP also could suppress the sterile phenotype if expressed in S.pombe pde1 cells, but overexpression of S.pombe TBP could do so very poorly. These observations suggest preliminarily that PP2C may counteract cAMP-dependent protein kinase in fission yeast cells, and that the heterologous TBPs and Dr1 may interfere with the general transcription factors of S.pombe so that the gene expression in the host cell becomes affirmative of sexual development. Furthermore, the identification of a Dr1-like protein in A.thaliana strongly argues for the ubiquity of this protein among eukaryotic genera and for a conserved mechanism to regulate transcription initiation that involves Dr1.