Zakaryan Rouzanna P, Gehring Heinz
Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
J Mol Biol. 2006 Oct 13;363(1):27-38. doi: 10.1016/j.jmb.2006.08.018. Epub 2006 Aug 11.
Ewing sarcoma (EWS) protein, a member of a large family of RNA-binding proteins, contains an N-terminal transcriptional activation domain (EAD) and a C-terminal RNA-binding domain (RBD). Due to its multifunctional properties EWS protein is involved in processes such as gene expression, RNA processing and transport, and cell signaling. Chimeric EWS proteins generated by chromosomal translocations cause malignant tumors. EWS protein is located predominantly in the nucleus, but was found also in the cytosol and associated with the cell membrane. The determinants responsible for the nuclear localization of the protein were as yet unknown. We identified the nuclear localization signal of EWS protein at its C terminus (C-NLS), which is required for the nuclear import and retention of the protein. The C-NLS sequence is conserved in related proto-oncoproteins suggesting an NLS function also in these proteins. Two arginine residues, due to their positive charge, a proline residue and a tyrosine residue are essential for C-NLS function. The nuclear localization of EWS protein is independent of the regions in RBD containing numerous arginine methylation sites, RNA-recognition and zinc finger motifs. Regions in EAD guide the subnuclear partition of EWS protein and contain another but different NLS that allows nucleocytoplasmic shuttling of the N-terminal domain.
尤因肉瘤（EWS）蛋白是RNA结合蛋白大家族的一员，包含一个N端转录激活结构域（EAD）和一个C端RNA结合结构域（RBD）。由于其多功能特性，EWS蛋白参与基因表达、RNA加工与转运以及细胞信号传导等过程。由染色体易位产生的嵌合EWS蛋白会引发恶性肿瘤。EWS蛋白主要位于细胞核中，但也在细胞质中被发现，并与细胞膜相关联。负责该蛋白核定位的决定因素尚不清楚。我们在EWS蛋白的C端鉴定出了其核定位信号（C-NLS），这是该蛋白核输入和滞留所必需的。C-NLS序列在相关原癌蛋白中保守，表明这些蛋白中也存在NLS功能。两个带正电荷的精氨酸残基、一个脯氨酸残基和一个酪氨酸残基对C-NLS功能至关重要。EWS蛋白的核定位独立于RBD中含有众多精氨酸甲基化位点、RNA识别和锌指基序的区域。EAD中的区域指导EWS蛋白的核内亚定位，并包含另一个不同的NLS，该NLS允许N端结构域进行核质穿梭。
