Functional small RNAs are generated from select miRNA hairpin loops in flies and mammals Journal Article

Authors: Okamura, K.; Ladewig, E.; Zhou, L.; Lai, E. C.
Article Title: Functional small RNAs are generated from select miRNA hairpin loops in flies and mammals
Abstract: In the canonical animal microRNA (miRNA) pathway, Drosha generates ~60- to 70-nucleotide pre-miRNA hairpins that are cleaved by Dicer into small RNA duplexes that load into Argonaute proteins, which retain a single mature strand in the active complex. The terminal loops of some miRNA hairpins regulate processing efficiency, but once liberated by Dicer, they are generally considered nonfunctional by-products. Here, we show that specific miRNA loops accumulate in effector Argonaute complexes in Drosophila and mediate miRNA-type repression. This was unexpected, since endogenous loading of Argonaute proteins was believed to occur exclusively via small RNA duplexes. Using in vitro assays, which recapitulate Argonaute-specific loop loading from synthetic pre-miRNAs and even single-stranded oligoribonucleotides corresponding to miRNA loops, we reveal that the loop-loading mechanism is distinct from duplex loading. We also show that miRNA loops loaded into the miRNA effector AGO1 are subject to 3' resection, and structure-function analyses indicate selectivity of loop loading. Finally, we demonstrate that select miRNA loops in mammals are similarly loaded into Argonaute complexes and direct target repression. Altogether, we reveal a conserved mechanism that yields functional RNAs from miRNA loop regions, broadening the repertoire of Argonaute-dependent regulatory RNAs and providing evidence for functionality of endogenous ssRNA species. © 2013 by Cold Spring Harbor Laboratory Press.
Keywords: controlled study; nonhuman; animal cell; mammalia; animals; mice; complex formation; microrna; genome-wide association study; drosophila; in vitro study; structure activity relation; animalia; gene expression regulation; conserved sequence; rna synthesis; mammal; gene repression; drosophila melanogaster; nucleic acid conformation; rna structure; micrornas; mammals; argonaute protein; drosophila proteins; short hairpin rna; argonaute 1 protein; double stranded rna; argonaute 2 protein; protein rna binding; single stranded rna; argonaute proteins; mirna hairpin loop; small rna loading
Journal Title: Genes and Development
Volume: 27
Issue: 7
ISSN: 0890-9369
Publisher: Cold Spring Harbor Laboratory Press  
Date Published: 2013-04-01
Start Page: 778
End Page: 792
Language: English
PROVIDER: scopus
PMCID: PMC3639418
PUBMED: 23535236
DOI: 10.1101/gad.211698.112
Notes: --- - "Export Date: 1 May 2013" - "CODEN: GEDEE" - ":doi 10.1101/gad.211698.112" - "Source: Scopus"
Citation Impact
MSK Authors
  1. Li Zhou
    3 Zhou
  2. Eric C Lai
    146 Lai
  3. Katsutomo Okamura
    26 Okamura
  4. Erik Manfred Ladewig
    15 Ladewig