A novel role for the nuclear localization signal in regulating hnRNP K protein stability in vivo

• Published in: Biochemical and biophysical research communications 2016-09, Vol.478 (2), p.772-776
• Main Authors: Hutchins, Erica J., Belrose, Jamie L., Szaro, Ben G.
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; Amino Acid Sequence; Animals; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Conserved Sequence; Embryo, Nonmammalian; Gene Expression; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Heterogeneous-Nuclear Ribonucleoproteins - genetics; Heterogeneous-Nuclear Ribonucleoproteins - metabolism; hnRNP K; KH domain; Mutagenesis, Site-Directed; Nuclear localization signal; Nuclear Localization Signals - genetics; Nuclear Localization Signals - metabolism; Protein Domains; Protein Isoforms - genetics; Protein Isoforms - metabolism; Protein Stability; Proteolysis; RABBIT TUBES; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; RNA-binding protein; Sequence Alignment; Sequence Homology, Amino Acid; SIGNALS; STABILITY; Ubiquitination; Xenopus; Xenopus laevis - embryology; Xenopus laevis - genetics; Xenopus laevis - metabolism
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2016.08.023

hnRNP K is a highly conserved nucleocytoplasmic shuttling protein, which associates with RNAs through synergistic binding via its three KH domains. hnRNP K is required for proper nuclear export and translational control of its mRNA targets, and these processes are controlled by hnRNP K's movement between subcellular compartments. Whereas the nuclear export and localization of hnRNP K that is associated with mRNP complexes has been well studied, the trafficking of hnRNP K that is unbound to mRNA has yet to be elucidated. To that end, we expressed an EGFP-tagged RNA binding-defective form of hnRNP K in intact Xenopus embryos, and found it was rapidly degraded in vivo. Deleting hnRNP K's nuclear localization signal (NLS), which contains two prospective ubiquitination sites, rescued the protein from degradation. These data demonstrate a novel activity for the NLS of hnRNP K in regulating the protein's stability in vivo when it is unbound to nucleic acids. •An RNA-binding mutant of Xenopus hnRNP K is degraded in vivo.•hnRNP K's nuclear localization signal contains two predicted ubiquitination sites.•Deletion of the nuclear localization signal rescues RNA-binding mutant degradation.