Large-scale induced fit recognition of an m(7)GpppG cap analogue by the human nuclear cap-binding complex.
The heterodimeric nuclear cap-binding complex (CBC) binds to the 5' cap structure of RNAs in the nucleus and plays a central role in their diverse maturation steps. We describe the crystal structure at 2.1 A resolution of human CBC bound to an m(7)GpppG cap analogue. Comparison with the structure of uncomplexed CBC shows that cap binding induces co-operative folding around the dinucleotide of some 50 residues from the N- and C-terminal extensions to the central RNP domain of the small subunit CBP20. The cap-bound conformation of CBP20 is stabilized by an intricate network of interactions both to the ligand and within the subunit, as well as new interactions of the CBP20 N-terminal tail with the large subunit CBP80. Although the structure is very different from that of other known cap-binding proteins, such as the cytoplasmic cap-binding protein eIF4E, specificity for the methylated guanosine again is achieved by sandwiching the base between two aromatic residues, in this case two conserved tyrosines. Implications for the transfer of capped mRNAs to eIF4E, required for translation initiation, are discussed.
Mazza
Catherine
C
European Molecular Biology Laboratory, Grenoble Outstation, c/o ILL, BP 181, F-38042 Grenoble cedex 9, France.
Segref
Alexandra
A
Mattaj
Iain W
IW
Cusack
Stephen
S
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D015226:Dinucleoside Phosphates / Q000737:chemistry* / Q000378:metabolism*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D039502:Nuclear Cap-Binding Protein Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010802:Phylogeny; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D021122:Protein Subunits; D012314:RNA Cap Analogs / Q000737:chemistry* / Q000378:metabolism*; D012315:RNA Caps / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
D015226:Dinucleoside Phosphates; D046911:Macromolecular Substances; D039502:Nuclear Cap-Binding Protein Complex; D021122:Protein Subunits; D012314:RNA Cap Analogs; D012315:RNA Caps; D011994:Recombinant Proteins; C062229:7-methyl-diguanosine triphosphate