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Updated: Aug 7, 2026
Growth Assays to Assess Polyglutamine Toxicity in Yeast
Published on: March 5, 2012
Flanking sequences profoundly alter polyglutamine toxicity in yeast
Martin L Duennwald1, Smitha Jagadish, Paul J Muchowski
1Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
Abstract:
Protein misfolding is the molecular basis for several human diseases. How the primary amino acid sequence triggers misfolding and determines the benign or toxic character of the misfolded protein remains largely obscure. Among proteins that misfold, polyglutamine (polyQ) expansion proteins provide an interesting case: Each causes a distinct neurodegenerative disease that selectively affects different neurons. However, all are broadly expressed and most become toxic when the glutamine expansion exceeds approximately 39 glutamine residues. The disease-causing polyQ expansion proteins differ profoundly in the amino acids flanking the polyQ region. We therefore hypothesized that these flanking sequences influence the specific toxic character of each polyQ expansion protein. Using a yeast model, we find that sequences flanking the polyQ region of human huntingtin exon I can convert a benign protein to a toxic species and vice versa. Further, we observe that flanking sequences can direct polyQ misfolding to at least two morphologically distinct types of polyQ aggregates. Very tight aggregates always are benign, whereas amorphous aggregates can be toxic. We thereby establish a previously undescribed systematic characterization of the influence of flanking amino acid sequences on polyQ toxicity.
Insights
Flanking amino acid sequences significantly influence polyglutamine (polyQ) protein toxicity and aggregation. These sequences can convert benign polyQ proteins into toxic forms and vice versa, impacting neurodegenerative disease.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Protein misfolding is central to human diseases.
- The role of primary amino acid sequence in protein misfolding and toxicity is unclear.
- Polyglutamine (polyQ) expansion proteins cause distinct neurodegenerative diseases.
Purpose of the Study:
- To investigate how flanking amino acid sequences influence polyQ protein toxicity.
- To determine if flanking sequences affect the aggregation morphology of polyQ proteins.
- To characterize the impact of flanking sequences on polyQ protein aggregation and toxicity.
Main Methods:
- Utilized a yeast model system.
- Studied the effects of flanking sequences on human huntingtin exon I polyQ region.
- Analyzed the morphology of polyQ aggregates.
Main Results:
- Flanking sequences can alter the toxicity of polyQ proteins, converting benign to toxic and vice versa.
- Flanking sequences direct polyQ misfolding into distinct aggregate types.
- Tightly packed aggregates were benign, while amorphous aggregates were toxic.
Conclusions:
- Amino acid sequences flanking the polyQ region play a critical role in determining polyQ protein toxicity.
- Flanking sequences modulate the specific toxic character of polyQ expansion proteins.
- This study establishes a systematic characterization of flanking sequence influence on polyQ toxicity and aggregation.
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