title: Distinct hydrophobic "patches" in the N- and C-tails of beta-catenin contribute to nuclear transport.
abstract: β-catenin is a key mediator of Wnt signaling and its deregulated nuclear accumulation can drive cancer progression. While the central armadillo (Arm) repeats of β-catenin stimulate nuclear entry, the N- and C-terminal "tail" sequences are thought to regulate turnover and transactivation. We show here that the N- and C-tails are also potent transport sequences. The unstructured tails of β-catenin, when individually fused to a GFP-reporter, could enter and exit the nucleus rapidly in live cells. Proximity ligation assays and pull-down assays identified a weak interaction between the tail sequences and the FG-repeats of nucleoporins, consistent with a possible direct translocation of β-catenin through the nuclear pore complex. Extensive alanine mutagenesis of the tail sequences revealed that nuclear translocation of β-catenin was dependent on specific uniformly distributed patches of hydrophobic residues, whereas the mutagenesis of acidic amino acids had no effect. Moreover, the mutation of hydrophobic patches within the N-tail and C-tail of full length β-catenin reduced nuclear transport rate and diminished its ability to activate transcription. We propose that the tail sequences can contribute to β-catenin transport and suggest a possible similar role for hydrophobic unstructured regions in other proteins.
authors.affiliation: Center for Cancer Research, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW 2145, Australia.
authors.forename: Manisha
authors.initials: M
authors.lastname: Sharma
authors.affiliation: Center for Cancer Research, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW 2145, Australia.
authors.forename: Cara
authors.initials: C
authors.lastname: Jamieson
authors.affiliation: Center for Cancer Research, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW 2145, Australia.
authors.forename: Christina
authors.initials: C
authors.lastname: Lui
authors.affiliation: Center for Cancer Research, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW 2145, Australia. Electronic address: beric.henderson@sydney.edu.au.
authors.forename: Beric R
authors.initials: BR
authors.lastname: Henderson
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D002470:Cell Survival; D036681:Fluorescence Recovery After Photobleaching; D057809:HEK293 Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D051379:Mice; D016296:Mutagenesis / Q000235:genetics; D041681:NIH 3T3 Cells; D022022:Nuclear Pore / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D013329:Structure-Activity Relationship; D015533:Transcriptional Activation / Q000235:genetics; D051176:beta Catenin / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D028861:Nuclear Pore Complex Proteins; D051176:beta Catenin
keywords: Beta-catenin; Fluorescence recovery after photobleaching; Live cell imaging; Nuclear pore; Nuclear transport; Wnt signaling