Proofreading of single nucleotide insertion/deletion replication errors analyzed by MALDI-TOF mass spectrometry assay

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Small nucleotide insertion/deletion (indel) errors are common DNA replication errors.
• Repeated DNA sequences are susceptible to slippage, increasing indel error frequency.
• Proofreading and DNA mismatch repair are crucial for maintaining genetic fidelity.

Purpose of the Study:

• To measure the efficiency of Klenow polymerase (KF) proofreading for indel errors.
• To investigate how indel error position affects KF proofreading.
• To understand the mechanisms of polymerase-template interactions in error correction.

Main Methods:

• MALDI-TOF mass spectrometry (MS) was used to analyze KF proofreading.
• Non-labeled, non-radio-isotopic oligonucleotide primers with indel errors were used.
• Proofreading efficiency was assessed based on KF-modified mass changes of the primer.

Main Results:

• KF efficiently proofread indel errors located 1-5 nucleotides from the primer terminus.
• Indels at 6 nucleotides from the 3' end were partially corrected and extended.
• Indels located 7-9 nucleotides from the primer terminus escaped proofreading and were elongated.

Conclusions:

• The position of indel errors relative to the primer terminus significantly influences Klenow polymerase proofreading efficiency.
• Understanding these positional effects is key to comprehending DNA replication fidelity mechanisms.
• Further structural analysis can elucidate polymerase-primer-template interactions during error correction.