Composition and functional characterization of the yeast spliceosomal penta-snRNP. |
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Authors: | Scott W Stevens Daniel E Ryan Helen Y Ge Roger E Moore Mary K Young Terry D Lee John Abelson |
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Institution: | California Institute of Technology, Division of Biology 147-75, Pasadena, CA 91125, USA. |
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Abstract: | Pre-mRNA introns are spliced in a macromolecular machine, the spliceosome. For each round of splicing, the spliceosome assembles de novo in a series of ATP-dependent steps involving numerous changes in RNA-RNA and RNA-protein interactions. As currently understood, spliceosome assembly proceeds by addition of discrete U1, U2, and U4/U6*U5 snRNPs to a pre-mRNA substrate to form functional splicing complexes. We characterized a 45S yeast penta-snRNP which contains all five spliceosomal snRNAs and over 60 pre-mRNA splicing factors. The particle is functional in extracts and, when supplied with soluble factors, is capable of splicing pre-mRNA. We propose that the spliceosomal snRNPs associate prior to binding of a pre-mRNA substrate rather than with pre-mRNA via stepwise addition of discrete snRNPs. |
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