CGG repeats trigger translational frameshifts that generate aggregation-prone chimeric proteins.

Area of Science:

• Molecular Biology
• Neuroscience
• Genetics

Background:

• CGG repeat expansions in the FMR1 gene's 5'UTR are the cause of Fragile X-associated tremor/ataxia syndrome (FXTAS).
• These repeats form RNA secondary structures, leading to RAN translation and the production of toxic, aggregate-prone peptides.
• These peptides accumulate in neuronal intranuclear inclusions, contributing to neurotoxicity.

Purpose of the Study:

• To investigate the mechanism of toxicity associated with CGG repeat expansions in FXTAS.
• To determine the role of translational frameshifting in the production of toxic peptides.
• To analyze the aggregation and toxicity of chimeric peptides produced by RAN translation.

Main Methods:

• Constructing reporter genes with CGG repeats and non-repetitive sequences.
• Analyzing translation products using techniques to detect RAN translation and frameshifting.
• Assessing peptide aggregation and toxicity in cultured rodent neurons.

Main Results:

• FMRpolyG, the primary RAN translation product, showed reduced toxicity when generated from non-repetitive sequences.
• A +1 translational frameshift was observed within the CGG repeat sequence, shifting from the arginine to the glycine reading frame.
• Short chimeric arginine/glycine peptides aggregated differently and induced toxicity in neurons.

Conclusions:

• CGG repeats facilitate translational frameshifting during RAN translation.
• Chimeric peptides resulting from frameshifting contribute to the neurotoxicity observed in FXTAS.
• Understanding these mechanisms may lead to new therapeutic strategies for FXTAS and related disorders.