Transportin 3 (TNPO3)

TNPO3 is a nuclear import receptor for serine/arginine-rich (SR) proteins, which are essential precursor-mRNA splicing factors.By yeast 2-hybrid analysis using the RS domain of the E2 protein of human papillomavirus (HPV)-5 as bait, Lai et al. (2000) cloned a TNPO3 splice variant, TRNSR2, from a HeLa cell cDNA library. The deduced 923-amino acid TRNSR2 protein lacks 2 regions of about 30 amino acids each found in the TRNSR protein identified by Kataoka et al. (1999). Northern blot analysis detected ubiquitous expression of a 4.5-kb transcript, with highest expression in testis. Epitope-tagged TRNSR2 localized throughout transfected HeLa cells, but a mutant lacking the N-terminal region colocalized with splicing factor SC35 (SFRS2) in nuclear speckles.