Sachdev S, Bagchi S, Zhang D D, Mings A C, Hannink M
Biochemistry Department, University of Missouri-Columbia, Columbia, Missouri 65212, USA.
Mol Cell Biol. 2000 Mar;20(5):1571-82. doi: 10.1128/MCB.20.5.1571-1582.2000.
The inhibitor of kappa B alpha (IkappaBalpha) protein is able to shuttle between the cytoplasm and the nucleus. We have utilized a combination of in vivo and in vitro approaches to provide mechanistic insight into nucleocytoplasmic shuttling by IkappaBalpha. IkappaBalpha contains multiple functional domains that contribute to shuttling of IkappaBalpha between the cytoplasm and the nucleus. Nuclear import of IkappaBalpha is mediated by the central ankyrin repeat domain. Similar to previously described nuclear import pathways, nuclear import of IkappaBalpha is temperature and ATP dependent and is blocked by a dominant-negative mutant of importin beta. However, in contrast to classical nuclear import pathways, nuclear import of IkappaBalpha is independent of soluble cytosolic factors and is not blocked by the dominant-negative RanQ69L protein. Nuclear export of IkappaBalpha is mediated by an N-terminal nuclear export sequence. Nuclear export of IkappaBalpha requires the CRM1 nuclear export receptor and is blocked by the dominant-negative RanQ69L protein. Our results are consistent with a model in which nuclear import of IkappaBalpha is mediated through direct interactions with components of the nuclear pore complex, while nuclear export of IkappaBalpha is mediated via a CRM1-dependent pathway.
κBα抑制蛋白（IkappaBalpha）能够在细胞质和细胞核之间穿梭。我们运用了体内和体外相结合的方法，以深入了解IkappaBalpha在核质间穿梭的机制。IkappaBalpha包含多个功能域，这些功能域有助于其在细胞质和细胞核之间穿梭。IkappaBalpha的核输入由中央锚蛋白重复结构域介导。与先前描述的核输入途径相似，IkappaBalpha的核输入依赖于温度和ATP，并且被输入蛋白β的显性负突变体所阻断。然而，与经典的核输入途径不同，IkappaBalpha的核输入不依赖于可溶性胞质因子，并且不会被显性负性RanQ69L蛋白所阻断。IkappaBalpha的核输出由一个N端核输出序列介导。IkappaBalpha的核输出需要CRM1核输出受体，并且被显性负性RanQ69L蛋白所阻断。我们的结果与这样一种模型一致，即IkappaBalpha的核输入是通过与核孔复合体成分的直接相互作用介导的，而IkappaBalpha的核输出是通过依赖CRM1的途径介导的。
