Mazza C, Ohno M, Segref A, Mattaj I W, Cusack S
European Molecular Biology Laboratory, Grenoble Outstation, 6 rue Jules Horowitz, BP181, F-38042 9, Grenoble Cedex, France.
Mol Cell. 2001 Aug;8(2):383-96. doi: 10.1016/s1097-2765(01)00299-4.
The heterodimeric nuclear cap binding complex (CBC) binds to 5'-capped polymerase II transcripts. It enhances the efficiency of several mRNA maturation steps and is essential for U snRNA nuclear export in multicellular eukaryotes. The 2A crystal structure of human CBC shows that the large subunit, CBP80, comprises three domains, each containing consecutive helical hairpins and resembling the so-called MIF4G domain found in several other proteins involved in RNA metabolism. The small subunit, CPB20, has an RNP fold and associates with the second and third domains of CBP80. Site-directed mutagenesis revealed 4 residues of CBP20 which are critical for cap binding. A model for cap binding is proposed based on these results and the known mode of binding of RNA to RNP domains.
异二聚体核帽结合复合物（CBC）与5'-帽化的聚合酶II转录本结合。它提高了几个mRNA成熟步骤的效率，并且对于多细胞真核生物中U snRNA的核输出至关重要。人CBC的2A晶体结构表明，大亚基CBP80由三个结构域组成，每个结构域都包含连续的螺旋发夹，并且类似于在其他几种参与RNA代谢的蛋白质中发现的所谓MIF4G结构域。小亚基CPB20具有RNP折叠，并与CBP80的第二和第三结构域结合。定点诱变揭示了CPB20的4个对帽结合至关重要的残基。基于这些结果以及RNA与RNP结构域的已知结合模式，提出了一种帽结合模型。
