title: Microprocessor dynamics and interactions at endogenous imprinted C19MC microRNA genes.
abstract: Nuclear primary microRNA (pri-miRNA) processing catalyzed by the DGCR8-Drosha (Microprocessor) complex is highly regulated. Little is known, however, about how microRNA biogenesis is spatially organized within the mammalian nucleus. Here, we image for the first time, in living cells and at the level of a single microRNA cluster, the intranuclear distribution of untagged, endogenously-expressed pri-miRNAs generated at the human imprinted chromosome 19 microRNA cluster (C19MC), from the environment of transcription sites to single molecules of fully released DGCR8-bound pri-miRNAs dispersed throughout the nucleoplasm. We report that a large fraction of Microprocessor concentrates onto unspliced C19MC pri-miRNA deposited in close proximity to their genes. Our live-cell imaging studies provide direct visual evidence that DGCR8 and Drosha are targeted post-transcriptionally to C19MC pri-miRNAs as a preformed complex but dissociate separately. These dynamics support the view that, upon pri-miRNA loading and most probably concomitantly with Drosha-mediated cleavages, Microprocessor undergoes conformational changes that trigger the release of Drosha while DGCR8 remains stably bound to pri-miRNA.
authors.affiliation: Laboratoire de Biologie Moléculaire Eucaryote (LBME), Université Paul Sabatier (UPS), Université de Toulouse, 31000 Toulouse,  France.
authors.forename: Clément
authors.initials: C
authors.lastname: Bellemer
authors.forename: Marie-Line
authors.initials: ML
authors.lastname: Bortolin-Cavaillé
authors.forename: Ute
authors.initials: U
authors.lastname: Schmidt
authors.forename: Stig Mølgaard Rask
authors.initials: SM
authors.lastname: Jensen
authors.forename: Jørgen
authors.initials: J
authors.lastname: Kjems
authors.forename: Edouard
authors.initials: E
authors.lastname: Bertrand
authors.forename: Jérôme
authors.initials: J
authors.lastname: Cavaillé
mesh_terms: D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000235:genetics; D002470:Cell Survival; D002888:Chromosomes, Human, Pair 19 / Q000235:genetics*; D005786:Gene Expression Regulation; D056426:Genetic Loci / Q000235:genetics; D018392:Genomic Imprinting / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D005810:Multigene Family / Q000235:genetics*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D043244:Ribonuclease III / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C474043:DGCR8 protein, human; D035683:MicroRNAs; D011506:Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C517918:DROSHA protein, human; D043244:Ribonuclease III