Tóth E, Kulcsár P I, Fodor E, Ayaydin F, Kalmár L, Borsy A É, László L, Welker E
Institute of Biochemistry, Hungarian Academy of Sciences, Szeged, Hungary.
Biochim Biophys Acta. 2013 May;1833(5):1199-211. doi: 10.1016/j.bbamcr.2013.01.020. Epub 2013 Jan 27.
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.
朊病毒蛋白（PrP）——因其在传染性海绵状脑病中的核心作用而闻名——据报道具有两个核定位信号，并以各种形式定位于某些细胞的细胞核中。尽管这些数据表面上相互矛盾，但很明显，在健康或患病状态的细胞中都能发现核形式的朊病毒蛋白。在此我们报告，通过使用YFP-Sho构建体可视化发现，朊病毒蛋白超家族成员Shadoo（Sho）也存在于几种神经和非神经细胞系的细胞核中。这种核定位由包含（RXXX）8基序的小鼠Sho的（25-61）片段介导。生物信息学分析表明，（RXXX）n基序（n = 7-8）是哺乳动物Shadoo蛋白高度保守且具有特征性的部分。评估Sho是否通过易化转运进入细胞核的实验没有得出决定性结果：抑制细胞中需要能量的活性过程会消除核内而非核仁内的积累。然而，（RXXX）8基序无法介导超过核孔被动进入大小限制的大型融合构建体的核转运。追踪各种形式的Sho从翻译到细胞核的过程，并辨别PrP和Sho潜在的核功能，还需要进一步研究。
