The molecular basis for the regulation of the cap-binding complex by the importins.Dias, S.M., Wilson, K.F., Rojas, K.S., Ambrosio, A.L., Cerione, R.A.
(2009) Nat Struct Mol Biol 16: 930-937
- PubMed: 19668212
- DOI: https://doi.org/10.1038/nsmb.1649
- Primary Citation of Related Structures:
- PubMed Abstract:
The binding of capped RNAs to the cap-binding complex (CBC) in the nucleus, and their dissociation from the CBC in the cytosol, represent essential steps in RNA processing. Here we show how the nucleocytoplasmic transport proteins importin-alpha and importin-beta have key roles in regulating these events. As a first step toward understanding the molecular basis for this regulation, we determined a 2.2-A resolution X-ray structure for a CBC-importin-alpha complex that provides a detailed picture for how importin-alpha binds to the CBP80 subunit of the CBC. Through a combination of biochemical studies, X-ray crystallographic information and small-angle scattering experiments, we then determined how importin-beta binds to the CBC through its CBP20 subunit. Together, these studies enable us to propose a model describing how importin-beta stimulates the dissociation of capped RNA from the CBC in the cytosol following its nuclear export.
Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.