# Mismatch Repair in Gamma-Proteobacteria

> **NIH NIH R01** · OHIO STATE UNIVERSITY · 2020 · $327,600

## Abstract

MISMATCH REPAIR IN γ-PROTEOBACTERIA
PROJECT SUMMARY / ABSTRACT
Mismatch repair (MMR) is a highly conserved genome maintenance process that primarily resolves
polymerase misincorporation errors. Mutation of the MMR genes dramatically increase spontaneous
mutation rates and have been linked to adaptation as well as associated multi-drug resistance in several
pathogenic bacteria. MMR mutations in humans are the cause of the common human cancer
predisposition Lynch syndrome as well as numerous sporadic cancers.
MMR is an excision-resynthesis process that is initiated at a DNA strand break, which may be hundreds
to thousands of nucleotides away from the mismatch. The fidelity of MMR depends on establishing the
ssDNA break on the error-containing DNA strand. A subset of γ-proteobacteria, including E.coli and the
ESKAPE pathogens Klebsiella and Enterobacter, recently evolved DNA adenine methylation (Dam) and
MutH to introduce a ssDNA break onto the newly replicated strand containing a misincorporation error.
An important distinction between bacteria that utilize the Dam/MutH MMR Pathway and all other
organisms is that dam mutations are lethal in combination with mutation of several homologous
recombination genes (synthetic lethality). Similarly, mutations of MMR excision components are lethal in
combination with replication editing gene mutations. The mechanisms that lead to MMR-dependent
synthetic lethality are largely hypothetical.
Deterministic models have historically underpinned MMR mechanisms, where definite complexes and
progressions are proposed to complete the biochemical events. Using newly developed single molecule-
imaging techniques we showed that the initial steps of MMR rely on random DNA diffusion mechanics
that are modulated by the two most highly conserved MMR proteins in terrestrial biology, MutS and MutL.
This new application will test the hypothesis that the entire multi-component MMR excision process is
Stochastic (fully governed by random processes; the complete opposite of Deterministic). Understanding
such biochemical randomness should impact future research and therapeutic strategies targeting MMR.
We propose to use real-time single molecule imaging in vitro and in vivo to resolve the mechanics of
E.coli MMR and its role in synthetic lethality. The Specific Aims are: 1.) quantitative biophysical imaging
of individual MMR component activities, 2.) visualization of the complete MMR excision reaction on
single mismatched DNA molecules, and 3.) analysis of MMR component interactions in live cells.

## Key facts

- **NIH application ID:** 9928073
- **Project number:** 5R01GM129764-02
- **Recipient organization:** OHIO STATE UNIVERSITY
- **Principal Investigator:** Richard Fishel
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $327,600
- **Award type:** 5
- **Project period:** 2019-05-15 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9928073

## Citation

> US National Institutes of Health, RePORTER application 9928073, Mismatch Repair in Gamma-Proteobacteria (5R01GM129764-02). Retrieved via AI Analytics 2026-06-11 from https://api.ai-analytics.org/grant/nih/9928073. Licensed CC0.

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