Leucine-rich nuclear export signal (NES)
Short leucine-rich peptide that marks a protein for export from the nucleus to the cytoplasm through the export receptor CRM1. Fused to a protein of interest, it moves the protein out of the nucleus, and it is used to restrict a reporter or effector to the cytoplasm or to oppose a nuclear localization signal on the same protein.
Characteristics
Leucine-rich NESs are used by a wide range of proteins to leave the nucleus, and many are recognized by the export receptor CRM1. Experimentally validated NESs are collected in NESbase, which records whether each signal is necessary and sufficient for export and whether CRM1 mediates it. In the AQUA cloning test construct, an NES fused to the C-terminus of EGFP was paired with a nuclear localization signal on mCherry to give distinct subcellular localizations of the two reporters.
Applications: C-terminal fusion to a fluorescent reporter to confine it to the cytoplasm, as in the EGFP-NES / mCherry-NLS bicistronic expression control used to test AQUA cloning. Combined with a nuclear localization signal on the same cargo to set nuclear-cytoplasmic distribution.
Limitations: Export activity depends on the individual NES sequence and on its context in the cargo, so a given NES does not export every protein equally. The signal acts through the export receptor CRM1, and a cargo that also carries a strong nuclear localization signal shuttles between compartments instead of staying cytoplasmic.
Sequence
References
- T. la Cour (2003). NESbase version 1.0: a database of nuclear export signals. Nucleic Acids Res - la Cour 2003 NESbase
- Beyer et al. (2015). AQUA Cloning: A Versatile and Simple Enzyme-Free Cloning Approach. PLoS ONE - Beyer 2015 AQUA Cloning