Developing the use of mismatch binding proteins for discovering rare somatic mutations

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Presymptomatic cancer screening is crucial for early intervention.
• Detecting rare, unknown somatic mutations in human fluids is a significant challenge.
• Mismatch binding proteins offer a potential strategy for enriching mutant DNA sequences.

Purpose of the Study:

• To evaluate the efficacy of a maltose binding protein-TaqMutS (MBP-MutS) fusion protein for enriching DNA heteroduplexes containing rare mutations.
• To assess the feasibility of using this method for presymptomatic cancer screening from biological fluids.

Main Methods:

• Constructed and utilized a MBP-MutS fusion protein.
• Created synthetic DNA heteroduplexes with single nucleotide mismatches or deletions.
• Mixed heteroduplexes with homoduplexes at low ratios and applied enrichment using MBP-MutS.
• Analyzed enrichment efficiency using capillary DNA sequencing.

Main Results:

• MBP-MutS enriched single base deletion oligonucleotides by a factor of 29 and mismatch oligonucleotides by a factor of 2.
• N-1 oligonucleotide synthesis fragments were enriched more effectively than mismatches, potentially interfering with mismatch enrichment.
• Standard purification methods (HPLC, PAGE) did not remove these interfering N-1 fragments.

Conclusions:

• The MBP-MutS fusion protein demonstrates potential for enriching specific DNA mutations.
• Interference from synthetic DNA impurities (N-1 fragments) presents a significant obstacle for reliable mismatch mutation enrichment.
• Further research into novel purification strategies or alternative approaches is necessary to overcome these limitations for clinical application.