Cloning and chromosomal localization of Drosophila cDNA encoding the catalytic subunit of protein phosphatase 1α. High conservation between mammalian and insect sequences

A 1.2‐kb clone containing the full coding sequence of a protein phosphatase 1 catalytic subunit has been isolated from a Drosophila head cDNA library. It encodes a polypeptide of 302 amino acids with a molecular mass of 34.5 kDa. The predicted protein sequence is 92% identical (94% similar) to rabbit protein phosphatase 1α (PP‐1α) demonstrating strict conservation of the phosphatase catalytic subunit over a considerable evolutionary distance. Abundant 1.6‐kb and 2.5‐kb mRNA transcripts were detected troughout Drosophila development. The clone hybridised to four sites on Drosophila salivary gland polytene chromosomes. The major site is at 87B6‐12 on the right arm of chromosome 3. In addition, there are three secondary sites, one on the same chromosome at 96A2‐5 and two on the X chromosome at 9C1‐2 and 13C1‐2. Isolation of a further cDNA clone, hybridising to 9C1‐2 and encoding part of the catalytic subunit 88% similar to Drosophila PP‐1α, proves the existence of at least two transcriptionally active genes for protein phosphatase 1