Modulation of trinucleotide repeat instability by DNA polymerase β polymorphic variant R137Q

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Trinucleotide repeat (TNR) instability is linked to neurodegenerative diseases and cancer.
• DNA base excision repair (BER), particularly DNA polymerase β (pol β), is crucial for managing somatic TNR instability.
• Polymorphisms in BER enzymes and cofactors can modulate their function and impact TNR instability.

Purpose of the Study:

• To investigate the effect of the pol βR137Q polymorphic variant on TNR instability.
• To understand how pol βR137Q influences DNA repair mechanisms related to TNR stability.

Main Methods:

• Studied the DNA synthesis activity of the pol βR137Q variant during BER.
• Analyzed the interaction of pol βR137Q with DNA structures, including looped templates, during repair.

Main Results:

• The pol βR137Q variant exhibits reduced DNA synthesis activity, promoting TNR deletion during BER.
• This weak polymerase activity allows pol βR137Q to bypass small loops, facilitating TNR deletion, similar to wild-type pol β.
• The study found no evidence suggesting an elevated risk for TNR-associated diseases in carriers of the pol βR137Q variant.

Conclusions:

• The pol βR137Q variant's impaired DNA synthesis activity plays a role in TNR deletion during BER.
• Individuals with the pol βR137Q variant are unlikely to have a higher risk for diseases associated with TNR instability.