title: CGG Repeat-Associated Non-AUG Translation Utilizes a Cap-Dependent Scanning Mechanism of Initiation to Produce Toxic Proteins.
abstract: Repeat-associated non-AUG (RAN) translation produces toxic polypeptides from nucleotide repeat expansions in the absence of an AUG start codon and contributes to neurodegenerative disorders such as ALS and fragile X-associated tremor/ataxia syndrome. How RAN translation occurs is unknown. Here we define the critical sequence and initiation factors that mediate CGG repeat RAN translation in the 5' leader of fragile X mRNA, FMR1. Our results reveal that CGG RAN translation is 30%-40% as efficient as AUG-initiated translation, is m(7)G cap and eIF4E dependent, requires the eIF4A helicase, and is strongly influenced by repeat length. However, it displays a dichotomous requirement for initiation site selection between reading frames, with initiation in the +1 frame, but not the +2 frame, occurring at near-cognate start codons upstream of the repeat. These data support a model in which RAN translation at CGG repeats uses cap-dependent ribosomal scanning, yet bypasses normal requirements for start codon selection.
authors.affiliation: Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Kearse
authors.affiliation: Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Katelyn M
authors.initials: KM
authors.lastname: Green
authors.affiliation: Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Veterans Affairs Medical Center, Ann Arbor, MI 48105, USA.
authors.forename: Amy
authors.initials: A
authors.lastname: Krans
authors.affiliation: Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Caitlin M
authors.initials: CM
authors.lastname: Rodriguez
authors.affiliation: Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Alexander E
authors.initials: AE
authors.lastname: Linsalata
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Aaron C
authors.initials: AC
authors.lastname: Goldstrohm
authors.affiliation: Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Veterans Affairs Medical Center, Ann Arbor, MI 48105, USA; Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA. Electronic address: petertod@umich.edu.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Todd
mesh_terms: D039561:Eukaryotic Initiation Factor-4E / Q000235:genetics / Q000378:metabolism; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000096:biosynthesis* / Q000235:genetics*; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D018965:Frameshifting, Ribosomal; D017930:Genes, Reporter; D020022:Genetic Predisposition to Disease; D006367:HeLa Cells; D006801:Humans; D009410:Nerve Degeneration; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D016366:Open Reading Frames; D010641:Phenotype; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D024363:Transcription Initiation Site; D014162:Transfection; D019680:Trinucleotide Repeat Expansion; D018911:Trinucleotide Repeats
chemical_list: D039561:Eukaryotic Initiation Factor-4E; D051860:Fragile X Messenger Ribonucleoprotein 1; D012333:RNA, Messenger; C497683:FMR1 protein, human