Interactions between small nuclear ribonucleoprotein particles in formation of spliceosomes.
Electrophoretic separation of ribonucleoprotein particles in a nondenaturing gel was used to analyze the splicing of mRNA precursors. Early in the reaction, a complex formed consisting of the U2 small nuclear ribonucleoprotein particle (snRNP) bound to sequences upstream of the 3' splice site. This complex is modeled as a precursor of a larger complex, the spliceosome, which contains U2, U4/6, and U5 snRNPs. Conversion of the U2 snRNP-precursor RNA complex to the spliceosome probably involves binding of a single multi-snRNP particle containing U4/6 and U5 snRNPs. The excised intron was released in a complex containing U5, U6, and probably U2 snRNPs. Surprisingly, U4 snRNP was not part of the intron-containing complex, suggesting that U4/6 snRNP disassembles and assembles during splicing. Subsequently, the reassembled U4/6 snRNP would associate with U5 snRNP and participate in de novo spliceosome formation. U1 snRNP was not detected in any of the splicing complexes.
D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D009694:Nucleic Acid Precursors / Q000378:metabolism*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism*; D012342:RNA, Small Nuclear / Q000502:physiology*; D012261:Ribonucleoproteins / Q000502:physiology*; D017411:Ribonucleoproteins, Small Nuclear
D046911:Macromolecular Substances; D009694:Nucleic Acid Precursors; D012333:RNA, Messenger; D012342:RNA, Small Nuclear; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear