CUG initiation and frameshifting enable production of dipeptide repeat proteins from ALS/FTD C9ORF72 transcripts.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29323119.
- Also identified by DOI 10.1038/s41467-017-02643-5 and PMC identifier 5764992.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Expansion of G<sub>4</sub>C<sub>2</sub> repeats in the C9ORF72 gene is the most prevalent inherited form of amyotrophic lateral sclerosis and frontotemporal dementia. Expanded transcripts undergo repeat-associated non-AUG (RAN) translation producing dipeptide repeat proteins from all reading frames. We determined cis-factors and trans-factors influencing translation of the human C9ORF72 transcripts. G<sub>4</sub>C<sub>2</sub> translation operates through a 5'-3' cap-dependent scanning mechanism, requiring a CUG codon located upstream of the repeats and an initiator Met-tRNA<sup>Met</sup><sub>i</sub>. Production of poly-GA, poly-GP, and poly-GR proteins from the three frames is influenced by mutation of the same CUG start codon supporting a frameshifting mechanism. RAN translation is also regulated by an upstream open reading frame (uORF) present in mis-spliced C9ORF72 transcripts. Inhibitors of the pre-initiation ribosomal complex and RNA antisense oligonucleotides selectively targeting the 5'-flanking G<sub>4</sub>C<sub>2</sub> sequence block ribosomal scanning and prevent translation. Finally, we identified an unexpected affinity of expanded transcripts for the ribosomal subunits independently from translation.
Medical subject headings
- Amyotrophic Lateral Sclerosis
- C9orf72 Protein
- Frameshifting, Ribosomal
- Frontotemporal Dementia
- Peptide Chain Initiation, Translational