title: Mechanism of allele-selective inhibition of huntingtin expression by duplex RNAs that target CAG repeats: function through the RNAi pathway.
abstract: Huntington's disease is an incurable neurodegenerative disorder caused by expansion of a CAG trinucleotide repeat within one allele of the huntingtin (HTT) gene. Agents that block expression of mutant HTT and preserve expression of wild-type HTT target the cause of the disease and are an alternative for therapy. We have previously demonstrated that mismatch-containing duplex RNAs complementary to the expanded trinucleotide repeat are potent and allele-selective inhibitors of mutant HTT expression, but the mechanism of allele selectivity was not explored. We now report that anti-CAG duplex RNA preferentially recruits argonaute 2 (AGO2) to mutant rather than wild-type HTT mRNA. Efficient inhibition of mutant HTT protein expression requires less AGO2 than needed for inhibiting wild-type expression. In contrast, inhibiting the expression of mutant HTT protein is highly sensitive to reduced expression of GW182 (TNRC6A) and its two paralogs, a protein family associated with miRNA action. Allele-selective inhibition may involve cooperative binding of multiple protein-RNA complexes to the expanded repeat. These data suggest that allele-selective inhibition proceeds through an RNA interference pathway similar to that used by miRNAs and that discrimination between mutant and wild-type alleles of HTT mRNA is highly sensitive to the pool of AGO2 and GW182 family proteins inside cells.
authors.affiliation: Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center at Dallas, Dallas, TX 75390-9041, USA.
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Hu
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Dongbo
authors.initials: D
authors.lastname: Yu
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Chu
authors.forename: David R
authors.initials: DR
authors.lastname: Corey
mesh_terms: D000483:Alleles; D000818:Animals; D060565:Argonaute Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020137:Base Pair Mismatch; D002460:Cell Line; D002478:Cells, Cultured; D000071058:Huntingtin Protein; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics*; D059367:RNA Cleavage; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000502:physiology; D018911:Trinucleotide Repeats
chemical_list: C466422:AGO2 protein, human; D060565:Argonaute Proteins; C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D016601:RNA-Binding Proteins