U1 snRNP Cleavage and Polyadenylation Complex Spliceosomal Intermediate C Complex U4 snRNP Spliceosomal B Complex Formation of an intermediate Spliceosomal C complex Authored: Krainer, AR, 2003-06-05 08:30:23 Edited: Joshi-Tope, G, 0000-00-00 00:00:00 Pubmed11991638 Pubmed12176931 Reactome Database ID Release 4372130 Reactome, http://www.reactome.org ReactomeREACT_625 The spliceosomal C complex is a very short-lived intermediate; the splicing intermediates are rapidly converted to splicing products. Also, the spliced products are released very rapidly, and no complex containing both the splicing products has been isolated. Conversion of the spliceosomal B complex to the spliceosomal C complex requires ATP. The extensive base-pairing between the U4 and U6 snRNAs is disrupted during the formation of the C complex, which is thought to require helicase-type activity associated with the DEAD box factors.