Poly A Polymerase Beta (PAPOLb)

The transcription level of Papolb in a 2-week-old mouse was much lower than that of the general poly(A) polymerase gene, Pap (PAPOLA). The ratio of Papt to Pap was reversed in testis of a 4-week-old mouse. Transient expression in HeLa cells showed fluorescence-tagged Papolb protein in both the nucleus and the cytoplasm.The deduced 636-amino acid protein contains a catalytic core, an RNA-binding region, and a putative nuclear localization signal. Compared with human PAPII (PAPOLA), PAPT lacks about 100 C-terminal amino acids, including a second putative nuclear localization signal and part of the serine/threonine-rich domain. The 5-prime UTR of the PAPT cDNA shows features of a CpG island. The 4.5-kb transcript was expressed at much lower levels in other tissues examined.