title: Utilizing the GAAA tetraloop/receptor to facilitate crystal packing and determination of the structure of a CUG RNA helix.
abstract: Myotonic dystrophy type 1 (DM1) is a microsatellite expansion disorder caused by the aberrant expansion of CTG repeats in the 3'-untranslated region of the DMPK gene. When transcribed, the toxic RNA CUG repeats sequester RNA binding proteins, which leads to disease symptoms. The expanded CUG repeats can adopt a double-stranded structure, and targeting this helix is a therapeutic strategy for DM1. To improve our understanding of the 5'CUG/3'GUC motif and how it may interact with proteins and small molecules, we designed a short CUG helix attached to a GAAA tetraloop/receptor to facilitate crystal packing. Here we report the highest-resolution structure (1.95 Å) to date of a GAAA tetraloop/receptor and the CUG helix it was used to crystallize. Within the CUG helix, we identify two different forms of noncanonical U-U pairs and reconfirm that CUG repeats are essentially A-form. An analysis of all noncanonical U-U pairs in the context of CUG repeats revealed six different classes of conformations that the noncanonical U-U pairs are able to adopt.
authors.affiliation: Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, OR 97403, USA.
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Coonrod
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Lohman
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Berglund
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D006801:Humans; D009223:Myotonic Dystrophy / Q000235:genetics; D065636:Myotonin-Protein Kinase; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D012313:RNA / Q000737:chemistry*; D016601:RNA-Binding Proteins / Q000737:chemistry*; D019680:Trinucleotide Repeat Expansion; D018911:Trinucleotide Repeats
chemical_list: C585517:DMPK protein, human; D009838:Oligodeoxyribonucleotides; D016601:RNA-Binding Proteins; D012313:RNA; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases