6wx7
SOX2 bound to Importin-alpha 2
Structural highlights
FunctionIMA1_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. Publication Abstract from PubMedSOX (SRY-related HMG-box) transcription factors perform critical functions in development and cell differentiation. These roles depend on precise nuclear trafficking, with mutations in the nuclear targeting regions causing developmental diseases and a range of cancers. SOX protein nuclear localization is proposed to be mediated by two nuclear localization signals (NLSs) positioned within the extremities of the DNA-binding HMG-box domain and, although mutations within either cause disease, the mechanistic basis has remained unclear. Unexpectedly, we find here that these two distantly positioned NLSs of SOX2 contribute to a contiguous interface spanning 9 of the 10 ARM domains on the nuclear import adapter IMPalpha3. We identify key binding determinants and show this interface is critical for neural stem cell maintenance and for Drosophila development. Moreover, we identify a structural basis for the preference of SOX2 binding to IMPalpha3. In addition to defining the structural basis for SOX protein localization, these results provide a platform for understanding how mutations and post-translational modifications within these regions may modulate nuclear localization and result in clinical disease, and also how other proteins containing multiple NLSs may bind IMPalpha through an extended recognition interface. Structural basis for nuclear import selectivity of pioneer transcription factor SOX2.,Jagga B, Edwards M, Pagin M, Wagstaff KM, Aragao D, Roman N, Nanson JD, Raidal SR, Dominado N, Stewart M, Jans DA, Hime GR, Nicolis SK, Basler CF, Forwood JK Nat Commun. 2021 Jan 4;12(1):28. doi: 10.1038/s41467-020-20194-0. PMID:33397924[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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