CGG Repeat-Associated Non-AUG Translation Utilizes a Cap-Dependent Scanning Mechanism of Initiation to Produce Toxic Proteins

Michael G Kearse; Katelyn M Green; Amy Krans; Caitlin M Rodriguez; Alexander E Linsalata; Aaron C Goldstrohm; Peter K Todd

doi:10.1016/j.molcel.2016.02.034

CGG Repeat-Associated Non-AUG Translation Utilizes a Cap-Dependent Scanning Mechanism of Initiation to Produce Toxic Proteins

Mol Cell. 2016 Apr 21;62(2):314-322. doi: 10.1016/j.molcel.2016.02.034. Epub 2016 Mar 31.

Authors

Michael G Kearse¹, Katelyn M Green², Amy Krans³, Caitlin M Rodriguez⁴, Alexander E Linsalata², Aaron C Goldstrohm⁵, Peter K Todd⁶

Affiliations

¹ 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.
² 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.
³ Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Veterans Affairs Medical Center, Ann Arbor, MI 48105, USA.
⁴ 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.
⁵ Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
⁶ 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.

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.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Eukaryotic Initiation Factor-4E / genetics
Eukaryotic Initiation Factor-4E / metabolism
Fragile X Mental Retardation Protein / biosynthesis*
Fragile X Mental Retardation Protein / genetics*
Fragile X Syndrome / diagnosis
Fragile X Syndrome / genetics*
Fragile X Syndrome / pathology
Frameshifting, Ribosomal
Genes, Reporter
Genetic Predisposition to Disease
HeLa Cells
Humans
Nerve Degeneration*
Neurons / metabolism
Neurons / pathology
Open Reading Frames
Phenotype
Protein Biosynthesis*
RNA, Messenger / genetics*
RNA, Messenger / metabolism
Ribosomes / metabolism
Transcription Initiation Site
Transfection
Trinucleotide Repeat Expansion
Trinucleotide Repeats*

Substances

Eukaryotic Initiation Factor-4E
FMR1 protein, human
RNA, Messenger
Fragile X Mental Retardation Protein

Abstract

Publication types

MeSH terms

Substances

Grants and funding