title: A competitive regulatory mechanism discriminates between juxtaposed splice sites and pri-miRNA structures.
abstract: We have explored the functional relationships between spliceosome and Microprocessor complex activities in a novel class of microRNAs (miRNAs), named Splice site Overlapping (SO) miRNAs, whose pri-miRNA hairpins overlap splice sites. We focused on the evolutionarily conserved SO miR-34b, and we identified two indispensable elements for recognition of its 3' splice site: a branch point located in the hairpin and a downstream purine-rich exonic splicing enhancer. In minigene systems, splicing inhibition owing to exonic splicing enhancer deletion or AG 3'ss mutation increases miR-34b levels. Moreover, small interfering-mediated silencing of Drosha and/or DGCR8 improves splicing efficiency and abolishes miR-34b production. Thus, the processing of this 3' SO miRNA is regulated in an antagonistic manner by the Microprocessor and the spliceosome owing to competition between these two machineries for the nascent transcript. We propose that this novel mechanism is commonly used to regulate the relative amount of SO miRNA and messenger RNA produced from primary transcripts.
authors.affiliation: Human Molecular Genetics, International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149, Trieste, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Mattioli
authors.forename: Giulia
authors.initials: G
authors.lastname: Pianigiani
authors.forename: Franco
authors.initials: F
authors.lastname: Pagani
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D035683:MicroRNAs / Q000096:biosynthesis* / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011506:Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D011687:Purines / Q000032:analysis; D034622:RNA Interference; D022821:RNA Splice Sites; D016601:RNA-Binding Proteins; D038621:Regulatory Sequences, Ribonucleic Acid; D043244:Ribonuclease III / Q000037:antagonists & inhibitors / Q000235:genetics
chemical_list: C474043:DGCR8 protein, human; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D011506:Proteins; D011687:Purines; D022821:RNA Splice Sites; D016601:RNA-Binding Proteins; D038621:Regulatory Sequences, Ribonucleic Acid; C517918:DROSHA protein, human; D043244:Ribonuclease III