Isolation of a cDNA Encoding a Portion of the Cyclic Nucleotide Phosphodiesterase of Dictyostelium discoideum

Abstract

The cyclic nucleotide phosphodiesterase (phosphodiesterase) of Dictyostelium discoideum is one of a group of developmentally regulated proteins which enable cells to aggregate by chemotaxis during the early stages of development. We report the identification and DNA sequence of a cDNA clone encoding the amino-terminal region of the phosphodiesterase. The clone, pPD-3, was selected from a cDNA library created by priming first strand synthesis using a set of oligonucleotides with sequences predicted from the amino-terminal amino acid sequence of purified phosphodiesterase. The DNA sequence of pPD-3 encodes perfectly the available phosphodiesterase amino acid sequence, and pPD-3 selects an mRNA which can be translated into material recognized by phosphodiesterase antisera. The nucleotide sequence of pPD-3 indicates there are 49 amino acids, which contain a segment processing the characteristics of a signal peptide, that separate the amino-terminal residue identified in the purified protein from the methionine codon at which translation originates. DNA blot analysis demonstrates that the phosphodiesterase gene exists as a single copy in the nuclear genome. Analysis of RNA indicates that the phosphodiesterase transcript is 2.1 kb long, which is approximately 0.8 kb more than the minimum required to encode this protein.