Genomic organization and mapping of the gene encoding the PP2A B56γ regulatory subunit

Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase that regulates a wide variety of cellular processes. The enzymatic activity and intracellular localization of PP2A are determined by three distinct families of cellular regulatory subunits (B, B′, and B″). The B′ subunit, also known as B56, is the most diverse, consisting of five isoforms (α, β, γ, δ, and ε). The gene encoding B56γ has been designated as PPP2R5C and encodes three differentially spliced variants: B56γ1, -γ2, and -γ3. However, conflicting chromosomal loci have been reported in human genomic databases. The original cytogenetic mapping placed the gene on chromosome 3p21.3, whereas subsequent studies using radiation hybrid analysis localized PPP2R5C to chromosome 14q. In this study, by radiation hybrid mapping, FISH analysis, BAC clone sequencing, and RT-PCR analysis, we show that the functional gene PPP2R5C exists at 14q32.2 and gives rise to three splicing variants, B56γ1, -γ2, and -γ3, whereas a nonfunctional B56γ1 pseudogene, PPP2R5CP, is present at 3p21.3. We also report the genomic organization of both the functional gene and the pseudogene.