The highly conserved, N-terminal (RXXX)8 motif of mouse Shadoo mediates nuclear accumulation

• Published in: Biochimica et biophysica acta Vol. 1833; no. 5; pp. 1199 - 1211
• Main Authors: Tóth, E., Kulcsár, P.I., Fodor, E., Ayaydin, F., Kalmár, L., Borsy, A.É., László, L., Welker, E.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2013
• Subjects: (RXXX)n motif; Active Transport, Cell Nucleus; Amino Acid Motifs - genetics; Animals; Cell Nucleus - metabolism; Cell Nucleus - ultrastructure; Conserved Sequence - genetics; HeLa Cells; Humans; Mice; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Neurons - metabolism; Nuclear localization signal; Nuclear Localization Signals - metabolism; Nucleic acid binding; Prion protein; Prions - genetics; Prions - metabolism; Repetitive Sequences, Amino Acid - genetics; RGG-box; Shadoo; RT; Nuclear localization signal; CNS; NRS; QKI-5; GFP; DMEM; GPI anchor; NLS; RGG-box; snls; Sho; Prion protein; aa; FITC-BSA; PBS; SS; YFP; DEG; TTF-1; ER; (RXXX)n motif; ECL; PrP; (Cherry)4; Shadoo; Nucleic acid binding; (Cherry)2; SV40; HD; ATP; RPMI medium; β-Gal
• ISSN: 0167-4889; 0006-3002; 1879-2596; 1878-2434
• DOI: 10.1016/j.bbamcr.2013.01.020

The prion protein (PrP)—known for its central role in transmissible spongiform encephalopathies—has been reported to possess two nuclear localization signals and localize in the nuclei of certain cells in various forms. Although these data are superficially contradictory, it is apparent that nuclear forms of the prion protein can be found in cells in either the healthy or the diseased state. Here we report that Shadoo (Sho)—a member of the prion protein superfamily—is also found in the nucleus of several neural and non-neural cell lines as visualized by using an YFP-Sho construct. This nuclear localization is mediated by the (25-61) fragment of mouse Sho encompassing an (RXXX)8 motif. Bioinformatic analysis shows that the (RXXX)n motif (n=7-8) is a highly conserved and characteristic part of mammalian Shadoo proteins. Experiments to assess if Sho enters the nucleus by facilitated transport gave no decisive results: the inhibition of active processes that require energy in the cell, abolishes nuclear but not nucleolar accumulation. However, the (RXXX)8 motif is not able to mediate the nuclear transport of large fusion constructs exceeding the size limit of the nuclear pore for passive entry. Tracing the journey of various forms of Sho from translation to the nucleus and discerning the potential nuclear function of PrP and Sho requires further studies. ► Tagged forms of Shadoo show dual, plasma membrane and nuclear localization. ► The (RXXX)8 motif of Shadoo is capable of directing the protein to the nucleus. ► The arginines of the (RXXX)8 motif have a critical role in nuclear localization. ► Shadoo has a not yet identified binding partner in the nucleolus.