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.

Public Health Relevance

Many proteins are mislocalized in diseases such as amyotrophic lateral sclerosis and cancer. It is important to understand how proteins are targeted correctly since correcting protein mislocalization may be a valid disease therapy.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
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Ainsztein, Alexandra M
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University of Texas Sw Medical Center Dallas
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Fung, Ho Yee Joyce; Fu, Szu-Chin; Chook, Yuh Min (2017) Nuclear export receptor CRM1 recognizes diverse conformations in nuclear export signals. Elife 6:
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Fung, Ho Yee Joyce; Chook, Yuh Min (2014) Atomic basis of CRM1-cargo recognition, release and inhibition. Semin Cancer Biol 27:52-61

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