Abstract
Previously, we isolated a novel rice protein, IABP4, that is specifically bound to particular rice importinα protein whose expression is down-regulated by light. IABP4 consists of a long N-terminal tetratricopeptide repeat (TPR) domain, the presence of which implies activity to form a protein complex, and a small C-terminal domain that contains three putative nuclear localization signals (NLSs). However, there has been no direct evidence that IABP4 is nuclear-localized. Therefore, we examined the intracellular localization of green fluorescent protein (GFP)-IABP4 fusions in onion epidermal cells, and only the GFP-fusion with the C-terminal fragment containing three putative NLSs was exclusively localized in the nucleus. By further experiments, we identified the one among three putative NLSs as the functional NLS. However, because the GFP-fusion with the entire IABP4 protein failed to localize exclusively in the nucleus, we suppose that the N-terminal domain is involved in the control of intracellular localization of IABP4.
