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Cell Signal. 2008 Aug;20(8):1442-51. doi: 10.1016/j.cellsig.2008.03.012. Epub 2008 Apr 1.

NF-kappaB p52, RelB and c-Rel are transported into the nucleus via a subset of importin alpha molecules.

Author information

1
Department of Viral Diseases and Immunology, National Public Health Institute, FIN-00300, Helsinki, Finland. riku.fagerlund@ktl.fi

Abstract

In resting cells NF-kappaB transcription factors are retained in the cytoplasm as latent inactive complexes, until they are activated and rapidly transported into the nucleus. We show that all NF-kappaB proteins are imported into the nucleus via a subset of importin alpha isoforms. Our data indicate that the NF-kappaB components of the classical and alternative pathways have somewhat different specifities to importin alpha molecules. Based on the results from binding experiments of in vitro-translated and Sendai virus infection-induced or TNF-alpha-stimulated endogenous NF-kappaB proteins, it can be predicted that the specifity of NF-kappaB proteins to importin alpha molecules is different and changes upon the composition of the imported dimer. p52 protein binds directly to importin alpha3, alpha4, alpha5 and alpha6 and c-Rel binds to importin alpha5, alpha6 and alpha7 via a previously described monopartite nuclear localization signals (NLSs). Here we show that RelB, instead, has a bipartite arginine/lysine-rich NLS that mediates the binding of RelB to importin alpha5 and alpha6 and subsequent nuclear translocation of the protein. Moreover, we show that the nuclear import of p52/RelB heterodimers is mediated exclusively by the NLS of RelB. In addition, we found that the NLS of p52 mediates the nuclear import of p52/p65 heterodimers.

PMID:
18462924
DOI:
10.1016/j.cellsig.2008.03.012
[Indexed for MEDLINE]

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