Interfering with protein-protein interactions in the spliceosme

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Pre-mRNA splicing is carried out by an elaborate ribonucleoprotein (RNP) enzyme, the spliceosome, which is assembled anew on each pre-mRNA intron by the stepwise interaction of snRNPs and multiple non-snRNP splicing factors. During its maturation into a catalytically active RNP, the spliceosome is repeatedly remodeled, undergoing numerous compositional and conformational changes. Spliceosome maturation and catalysis are accompanied by profound rearrangements in the spliceosomal RNA and RNP networks and by the dynamic exchanges of more than 100 proteins. At present we have incomplete knowledge of the role of individual proteins or protein complexes and of the sequence of protein exchanges during spliceosome maturation and catalysis. Most likely, a large number of assembly intermediates exist in addition to the limited number of intermediates identified to date. In order to access novel and compositionally homogenous intermediates, we plan to develop and characterize small molecule inhibitors that interfere with particular spliceosomal protein-protein interactions. Inhibitors will be identified by three strategies: (1) Rational design based on crystal structures of protein complexes; (2) Targeted screening based on isolated protein pairs; (3) Targeted screening based on a protein recruitment assay. Initial hits will be improved by synthetic optimization aided by co-crystal structures of proteins in complex with inhibitors. The results obtained will not only help to elucidate the conformational dynamics of spliceosome assembly and catalysis but may also provide useful leads for the development of therapeutic spliceosome inhibitors.