4c0q
Transportin 3 in complex with Ran(Q69L)GTP
Structural highlights
DiseaseTNPO3_HUMAN Primary biliary cirrhosis;Autosomal dominant limb-girdle muscular dystrophy type 1F. FunctionTNPO3_HUMAN Seems to function in nuclear protein import as nuclear transport receptor. In vitro, mediates the nuclear import of splicing factor SR proteins RBM4, SFRS1 and SFRS2, by recognizing phosphorylated RS domains.[1] [2] [3] [4] Publication Abstract from PubMedTransportin 3 (Tnpo3, Transportin-SR2) is implicated in nuclear import of splicing factors and HIV-1 replication. Herein, we show that the majority of cellular Tnpo3 binding partners contain arginine-serine (RS) repeat domains and present crystal structures of human Tnpo3 in its free as well as GTPase Ran- and alternative splicing factor/splicing factor 2 (ASF/SF2)-bound forms. The flexible beta-karyopherin fold of Tnpo3 embraces the RNA recognition motif and RS domains of the cargo. A constellation of charged residues on and around the arginine-rich helix of Tnpo3 HEAT repeat 15 engage the phosphorylated RS domain and are critical for the recognition and nuclear import of ASF/SF2. Mutations in the same region of Tnpo3 impair its interaction with the cleavage and polyadenylation specificity factor 6 (CPSF6) and its ability to support HIV-1 replication. Steric incompatibility of the RS domain and RanGTP engagement by Tnpo3 provides the mechanism for cargo release in the nucleus. Our results elucidate the structural bases for nuclear import of splicing factors and the Tnpo3-CPSF6 nexus in HIV-1 biology. Structural basis for nuclear import of splicing factors by human Transportin 3.,Maertens GN, Cook NJ, Wang W, Hare S, Gupta SS, Oztop I, Lee K, Pye VE, Cosnefroy O, Snijders AP, Kewalramani VN, Fassati A, Engelman A, Cherepanov P Proc Natl Acad Sci U S A. 2014 Jan 21. PMID:24449914[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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