Bangs P, Burke B, Powers C, Craig R, Purohit A, Doxsey S
Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
J Cell Biol. 1998 Dec 28;143(7):1801-12. doi: 10.1083/jcb.143.7.1801.
Tpr is a 270-kD coiled-coil protein localized to intranuclear filaments of the nuclear pore complex (NPC). The mechanism by which Tpr contributes to the structure and function of the nuclear pore is currently unknown. To gain insight into Tpr function, we expressed the full-length protein and several subdomains in mammalian cell lines and examined their effects on nuclear pore function. Through this analysis, we identified an NH2-terminal domain that was sufficient for association with the nucleoplasmic aspect of the NPC. In addition, we unexpectedly found that the acidic COOH terminus was efficiently transported into the nuclear interior, an event that was apparently mediated by a putative nuclear localization sequence. Ectopic expression of the full-length Tpr caused a dramatic accumulation of poly(A)+ RNA within the nucleus. Similar results were observed with domains that localized to the NPC and the nuclear interior. In contrast, expression of these proteins did not appear to affect nuclear import. These data are consistent with a model in which Tpr is tethered to intranuclear filaments of the NPC by its coiled coil domain leaving the acidic COOH terminus free to interact with soluble transport factors and mediate export of macromolecules from the nucleus.
Tpr是一种270-kD的卷曲螺旋蛋白，定位于核孔复合体（NPC）的核内细丝。目前尚不清楚Tpr对核孔结构和功能的作用机制。为深入了解Tpr的功能，我们在哺乳动物细胞系中表达了全长蛋白和几个亚结构域，并检测了它们对核孔功能的影响。通过该分析，我们鉴定出一个NH2末端结构域，它足以与NPC的核质部分结合。此外，我们意外地发现酸性COOH末端能有效地转运到核内部，这一事件显然是由一个假定的核定位序列介导的。全长Tpr的异位表达导致核内poly(A)+ RNA大量积累。定位于NPC和核内部的结构域也观察到类似结果。相反，这些蛋白的表达似乎不影响核输入。这些数据与一个模型一致，即Tpr通过其卷曲螺旋结构域与NPC的核内细丝相连，使酸性COOH末端能够自由地与可溶性转运因子相互作用，并介导大分子从细胞核输出。
