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

Tóth, Eszter and Kulcsár, P. I. and Fodor, Elfrieda and Ayaydin, Ferhan and Kalmár, Lajos and Borsy, Adrienn Éva and László, Lajos and Welker, Ervin (2013) The highly conserved, N-terminal (RXXX)8 motif of mouse Shadoo mediates nuclear accumulation. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH, 1833 (5). pp. 1199-1211. ISSN 0167-4889

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Abstract

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.

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