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The molecular basis for the regulation of the cap-binding complex by the importins.

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.

SUBMITTER: Dias SM

PROVIDER: S-EPMC2782468 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

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The molecular basis for the regulation of the cap-binding complex by the importins.

Dias Sandra M G SM Wilson Kristin F KF Rojas Katherine S KS Ambrosio Andre L B AL Cerione Richard A RA

Nature structural & molecular biology 20090809 9

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 ...[more]

PMID: 19668212

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