Production of shorter mRNA for protein phosphatase 2A beta by alternative poly(A) addition

Two types of cDNA clones of protein phosphatase 2A beta, PP-2A beta L and PP-2A beta S, were isolated from a rat testis cDNA library. PP-2A beta L was 1.8 kb in length and corresponded to the 2.0 kb mRNA that is the major species expressed in somatic tissues. PP-2A beta S was 1.3 kb in length and corresponded to the 1.4 kb mRNA that is the major species expressed in germ cells of the testis. Nucleotide sequencing of these two clones revealed that their open reading frames were identical. The only difference between these two cDNAs was at the 3' non-coding region due to alternative poly(A) addition: the 1.8 kb cDNA had a consensus poly(A) addition signal, AATAAA, but the 1.3 kb cDNA had an unusual poly(A) addition signal, probably with the sequence AATATA. These data suggest that in germ cells there may be some mechanism that utilizes the specific poly(A) addition signal.