Structures and mechanisms of nuclear import and export

描述(申请人提供)：核仁蛋白？蛋白通过识别不同的核定位或输出信号(NLSS或NESS)来调节核质运输。虽然在人类中有19个已知的Kap，但目前只知道Kap？/Kap？1、Kap？2(或Transportin)和CRM1的三种信号。大多数其他KAP识别不同的序列，这些序列遮挡了它们信号的身份。该提案描述了进口系统Kap？2和Imp5/Kap121以及出口系统Kap CRM1的结构和生化分析。KAP？2通过其PY-NLSS介导RNA结合蛋白的核输入。我们对PY-NLS的发现和理解有助于发现一种导致肌萎缩侧索硬化症(ALS)亚型的PY-NLS缺陷。在这里，我们建议了解Kap？2在ALS中蛋白质错误定位和聚集中的作用。在另一个目标中，我们将把我们用来发现PY-NLS的结构、生化和生物信息学相结合的方法应用于Imp5/Kap121P途径，目的是发现一组特征来统一KAP识别的不同序列，从而揭示一类新的NLS。最后，我们将研究CRM1，它介导了数百种蛋白质的核输出；其中大多数是用小分子抑制剂Leptomycin B鉴定的。这项建议旨在确定CRM1如何介导Leptomycin B的结合抑制核输出的机制。

DESCRIPTION (provided by applicant): Karyopherin¿ proteins mediate nucleocytoplasmic transport through recognition of distinct nuclear localization or export signals (NLSs or NESs). Although there are 19 known Kaps in humans, only three classes of signals for Kap¿/Kap¿1, Kap¿2 (or Transportin) and CRM1, respectively, are known at this time. Most other Kaps recognize diverse sequences that occlude the identity of their signals. This proposal describes structural and biochemical analyses of import systems Kap¿2 and Imp5/Kap121 as well as the export-Kap CRM1. Kap¿2 mediates nuclear import of RNA binding proteins through their PY-NLSs. Our discovery and understanding of the PY-NLS contributed to the discovery of a defective PY-NLS that causes a subset of amyotrophic lateral sclerosis (ALS). Here, we propose to understand the role of Kap¿2 in protein mislocalization and aggregation in ALS. In another aim, we will apply the combined structural, biochemical and bioinformatics approach that we used to discover the PY-NLS to the Imp5/Kap121p pathway with the goal of discovering a set of characteristics to unify the diverse sequences recognized by the Kaps, hence revealing a new class of NLS. Finally, we will study CRM1, which mediates nuclear export of hundreds of proteins; most of them identified using the small molecule inhibitor Leptomycin B. This proposal aims to determine the mechanism of how CRM1 mediates conjugation of leptomycin B to inhibit nuclear export.