Structural highlights
Function
[IMA1_MOUSE] Functions in nuclear protein import as an adapter protein for nuclear receptor KPNB1. Binds specifically and directly to substrates containing either a simple or bipartite NLS motif. Docking of the importin/substrate complex to the nuclear pore complex (NPC) is mediated by KPNB1 through binding to nucleoporin FxFG repeats and the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, Ran binds to importin-beta and the three components separate and importin-alpha and -beta are re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran from importin. The directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus. [EBNA5_EBVB9] Plays an important role in the establishment of B-cell immortalization by acting as an EBNA2 coactivator. This transcriptional activation preferentially enhances the expression of the major viral protein LMP1. The interaction between EBNA-LP and host SP100 correlates with coactivation of EBNA2 and the relocalization of SP100 from PML nuclear bodies into nucleoplasm.
Publication Abstract from PubMed
Epstein-Barr virus EBNA-LP protein is a transcriptional coactivator of EBNA2. Efficient nuclear localization of EBNA-LP is essential for cooperation with EBNA2. Here, we report the crystal structure of the nuclear import adaptor importin-alpha1 bound to the nuclear localization signal (NLS) of EBNA-LP that shows EBNA-LP residues 44-RRVRRR-49 binding to the major NLS-binding site at the P0-P5 positions. In contrast to previously characterized classical NLSs that invariably have a basic residue [either lysine (in the vast majority of cases) or arginine] at the P2 position, the EBNA-LP NLS is unique in that it has valine at the P2 position. The loss of the critical P2 lysine (or arginine) is compensated by arginine at the P0 position in the EBNA-LP NLS.
Crystal structure of importin-alpha bound to the nuclear localization signal of Epstein-Barr virus EBNA-LP protein.,Nakada R, Matsuura Y Protein Sci. 2017 Apr 6. doi: 10.1002/pro.3173. PMID:28383161[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Nakada R, Matsuura Y. Crystal structure of importin-alpha bound to the nuclear localization signal of Epstein-Barr virus EBNA-LP protein. Protein Sci. 2017 Apr 6. doi: 10.1002/pro.3173. PMID:28383161 doi:http://dx.doi.org/10.1002/pro.3173
