cDNA cloning of BR gamma, a novel brain-specific isoform of the B regulatory subunit of type-2A protein phosphatase.

A cDNA clone for a novel isoform of the B regulatory subunit of type 2A protein phosphatase (BR) was isolated from a rat brain cDNA library by hybridization under low-stringency conditions with the BR beta cDNA fragment as a probe. The novel cDNA encodes a protein of 447 amino acids. The identities of amino acid sequences of the novel isoform with those of rat BR alpha and BR beta were 80% and 85%, respectively, with a unique sequence at the C-terminal. Since this isoform is thought to be encoded by a third gene for the B regulatory subunit, it was named BR gamma. The mRNA for BR gamma was 4.2 kb. The expression level of BR gamma was high in the brain and spinal cord of rats, and its expression was also detected in mouse and human brains, but in contrast to BR beta, it was not detected in the testes of rats or mice. Thus BR gamma is though to be a brain-specific isoform of the B regulatory subunit.