[Structural Study on the Molecular Interaction of the Pre-mRNA Splicing Factors]

Pre-mRNA splicing proceeds through two successive trans-esterification reactions: cleavage of the 5'-splice site by the nucleophilic attack from the conserved branch-site adenosine (step I), followed by release of the intron via nucleophilic attack of the 3' splice site by the phosphate group of the 5' splice site (step II). These processes are accomplished by the spliceosome, a dynamic macromolecular complex of the U1, U2, U4, U5 and U6 small nuclear ribonucleoproteins (snRNPs). Recognition of the 5' splice site, the branch point and the 3' splice site is mediated by the U1 and U2 snRNPs and the U2AF protein, respectively. The binding of these factors, and thereby the splicing pattern of the pre-mRNA, is regulated by hundreds of splicing-associated proteins, which bind near putative splicing sites in response to a variety of biological situations. Our group aims to elucidate the regulation mechanism of the first splicing step, using biochemical and structural approaches. In particular, we focus on the protein-protein and protein-RNA interactions involving the constitutive factors in step I (U1, U2snRNP and U2AF complex) and several splicing regulatory factors. Here, we summarize our findings in the context of recent advances in the field.