title: The DGCR8 RNA-binding heme domain recognizes primary microRNAs by clamping the hairpin.
abstract: Canonical primary microRNA transcripts (pri-miRNAs) are characterized by a ∼30 bp hairpin flanked by single-stranded regions. These pri-miRNAs are recognized and cleaved by the Microprocessor complex consisting of the Drosha nuclease and its obligate RNA-binding partner DGCR8. It is not well understood how the Microprocessor specifically recognizes pri-miRNA substrates. Here, we show that in addition to the well-known double-stranded RNA-binding domains, DGCR8 uses a dimeric heme-binding domain to directly contact pri-miRNAs. This RNA-binding heme domain (Rhed) directs two DGCR8 dimers to bind each pri-miRNA hairpin. The two Rhed-binding sites are located at both ends of the hairpin. The Rhed and its RNA-binding surface are important for pri-miRNA processing activity. Additionally, the heme cofactor is required for formation of processing-competent DGCR8-pri-miRNA complexes. Our study reveals a unique protein-RNA interaction central to pri-miRNA recognition. We propose a unifying model in which two DGCR8 dimers clamp a pri-miRNA hairpin using their Rheds.
authors.affiliation: Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Jen
authors.initials: J
authors.lastname: Quick-Cleveland
authors.affiliation: Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Jose P
authors.initials: JP
authors.lastname: Jacob
authors.affiliation: Molecular, Cell and Integrative Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Sara H
authors.initials: SH
authors.lastname: Weitz
authors.affiliation: Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Grant
authors.initials: G
authors.lastname: Shoffner
authors.affiliation: Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Senturia
authors.affiliation: Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA. Electronic address: fguo@mbi.ucla.edu.
authors.forename: Feng
authors.initials: F
authors.lastname: Guo
mesh_terms: D001665:Binding Sites; D006418:Heme / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C474043:DGCR8 protein, human; D035683:MicroRNAs; D016601:RNA-Binding Proteins; D006418:Heme