U12 Dependent Splicing Edited: Joshi-Tope, G, 0000-00-00 00:00:00 GENE ONTOLOGYGO:0000398 Pubmed10207048 Pubmed9149533 Reactome Database ID Release 4372165 Reactome, http://www.reactome.org ReactomeREACT_1753 The splicing of a subset of pre-mRNA introns occurs by a second pathway, designated the AT-AC or U12-dependent splicing pathway. AT-AC introns have highly conserved, non-canonical splice sites that are removed by the AT-AC spliceosome, which contains distinct snRNAs (U11, U12, U4atac, U6atac) that are structurally and functionally analogous to the major spliceosome. U5 snRNA as well as many of the protein factors appear to be conserved between the two spliceosomes. mRNA Splicing - Minor Pathway Formation of AT-AC B Complex Formation of AT-AC A complex ATAC spliceosome mediated 3' splice site cleavage, exon ligation Formation of AT-AC C complex ATAC spliceosome mediated Lariat formation,5' splice site cleavage PathwayStep46 PathwayStep45 PathwayStep42 PathwayStep43 PathwayStep44