NF-AT activation requires suppression of Crm1-dependent export by calcineurin.
Nuclear import of the NF-AT transcription factors during T-cell activation requires the calcium-activated phosphatase calcineurin, which unmasks nuclear-location signals on NF-AT. We show here that the nuclear import of NF-ATs is not sufficient to activate NF-AT target genes, as NF-ATs are subject to a futile cycling across the nuclear envelope owing to engagement with the exportin protein Crm1. Calcineurin suppresses this futile cycling by a non-catalytic mechanism involving the masking of nuclear export signals on NF-AT targeted by Crm1. This clustering of binding sites for calcineurin and Crml on NF-AT establishes an inherent competition between these molecules that imparts exquisite calcium sensitivity to the shuttling dynamics of the NF-AT transcription factors. Such a balance between nuclear import and export may regulate the action of other transcription factors.[1]References
- NF-AT activation requires suppression of Crm1-dependent export by calcineurin. Zhu, J., McKeon, F. Nature (1999) [Pubmed]
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