Msh2-Msh3 interferes with DNA metabolism in vivo

Medina-Rivera, M.; Sridharan, M.; Becker, J.; Phelps, S.; Lamb, N. A.; Kumar, C.; Cornaire, M.; Sutton, M. D.; Bielinsky, A. K.; Balakrishnan, L.; Surtees, J. A.

doi:10.1101/2022.09.06.506750

bioRxiv · 10.1101/2022.09.06.506750

Msh2-Msh3 interferes with DNA metabolism in vivo

Medina-Rivera, M.·Sridharan, M.·Becker, J.·Phelps, S.·Lamb, N. A.·Kumar, C.·Cornaire, M.·Sutton, M. D.·Bielinsky, A. K.·Balakrishnan, L.·Surtees, J. A.

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Abstract

Mismatch repair (MMR) is a highly conserved DNA repair pathway that safeguards the genome from errors in DNA replication. In Saccharomyces cerevisiae, two MutS homolog (Msh) complexes, Msh2-Msh3 or Msh2-Msh6, initiate MMR. Msh2-Msh3, the focus of this study, recognizes and directs repair of insertion/deletion loops (IDLs) up to ~17 nucleotides. Msh2-Msh3 also recognizes and binds distinct looped and branched DNA structures with varying affinities, thereby contributing to genome stability outside post-replicative MMR through homologous recombination, double-strand break repair (DSBR), and the DNA damage response. Msh2-Msh3 also promotes genome instability through trinucleotide repeat (TNR) expansions. This non-canonical activity is likely an unfortunate consequence of Msh2-Msh3s intrinsic ability to bind a wide range of DNA structures, including those formed with single-stranded (ss) TNR sequences. We previously demonstrated that Msh2-Msh3 binding to 5 ssDNA flap structures interfered with the in vitro binding and cleavage activities of the flap endonuclease Rad27 (Fen1 in mammals), which promotes 5 ssDNA flap processing during Okazaki fragment maturation (OFM) and long-patch base excision repair (LP-BER). Here we demonstrate that elevated Msh2-Msh3 levels interfere with DNA replication and LP-BER in vivo, consistent with the hypothesis that protein abundance and Msh3 ATPase activities are key drivers of Msh2-Msh3-mediated genomic instability.

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Medina-Rivera, M., Sridharan, M., Becker, J., Phelps, S., Lamb, N. A., Kumar, C., Cornaire, M., Sutton, M. D., Bielinsky, A. K., Balakrishnan, L., Surtees, J. A.. 2022-09-06. Msh2-Msh3 interferes with DNA metabolism in vivo. https://doi.org/10.1101/2022.09.06.506750

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