Human MutLα activates methylpurine DNA glycosylase to induce alkylation damage cytotoxicity
4 affiliations
- 1Department of Pathology and Immunology, Division of Laboratory and Genomic Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- 2Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- 3Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- 4Division of Biochemistry and Molecular Biology, Department of Biomedical Sciences, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, USA
Abstract
Alkylation chemotherapy is commonly used against tumors such as glioblastoma, yet resistance often develops through downregulation of mismatch repair (MMR). Previous work has established that loss of MMR prevents the excision of the thymine-containing strand across O6meG-T mismatches, thereby avoiding the futile repair cycle that ultimately leads to cell death. Here, we provide an alternative explanation to this prevailing mechanism of chemoresistance by MMR loss. We found that the MMR protein MutLα physically and functionally interacts with the base excision repair (BER) enzyme methylpurine DNA glycosylase (MPG), which processes common alkylation adducts, such as 7meG and 3meA. Biochemical reconstitution demonstrates that MutLα activates MPG glycosylase activity by promoting MPG substrate binding, and enhancing MPG release from the abasic site product, thereby facilitating enzyme turnover. This glycosylase stimulation requires ATP hydrolysis as well as the MLH1-interacting region on MPG. Both MutLα or its ability to interact with MPG promote the generation of alkylation-induced abasic sites in cells, which contribute to the cytotoxicity of methyl methanesulfonate (MMS), an SN2 alkylating agent that does not produce O6meG. Our results provide new insight into the mechanism of alkylation chemoresistance and uncover an unappreciated cross-talk between MMR and BER.
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BibTeX
@misc{ashour2026human,
title = {{Human MutLα activates methylpurine DNA glycosylase to induce alkylation damage cytotoxicity}},
author = {Mohamed E. Ashour and Ellissa Krekeler and Monika Chandan Bhowmik and Holland Kantar and Ning Tsao and Carlos Herrera-Montávez and Miaw-Sheue Tsai and Manal Zaher and Lyudmila Y. Kadyrova and Farid A. Kadyrov and Roberto Galletto and Nima Mosammaparast},
howpublished = {Genes \& Development},
year = {2026},
month = nov,
doi = {10.1101/gad.353661.126},
url = {https://doi.org/10.1101/gad.353661.126},
note = {CC BY-NC 4.0},
}
RIS
TY - UNPB
TI - Human MutLα activates methylpurine DNA glycosylase to induce alkylation damage cytotoxicity
AU - Mohamed E. Ashour
AU - Ellissa Krekeler
AU - Monika Chandan Bhowmik
AU - Holland Kantar
AU - Ning Tsao
AU - Carlos Herrera-Montávez
AU - Miaw-Sheue Tsai
AU - Manal Zaher
AU - Lyudmila Y. Kadyrova
AU - Farid A. Kadyrov
AU - Roberto Galletto
AU - Nima Mosammaparast
PY - 2026
DA - 2026/11/01
PB - Genes & Development
DO - 10.1101/gad.353661.126
UR - https://doi.org/10.1101/gad.353661.126
AB - Alkylation chemotherapy is commonly used against tumors such as glioblastoma, yet resistance often develops through downregulation of mismatch repair (MMR). Previous work has established that loss of MMR prevents the excision of the thymine-containing strand across O6meG-T mismatches, thereby avoiding the futile repair cycle that ultimately leads to cell death. Here, we provide an alternative explanation to this prevailing mechanism of chemoresistance by MMR loss. We found that the MMR protein MutLα physically and functionally interacts with the base excision repair (BER) enzyme methylpurine DNA glycosylase (MPG), which processes common alkylation adducts, such as 7meG and 3meA. Biochemical reconstitution demonstrates that MutLα activates MPG glycosylase activity by promoting MPG substrate binding, and enhancing MPG release from the abasic site product, thereby facilitating enzyme turnover. This glycosylase stimulation requires ATP hydrolysis as well as the MLH1-interacting region on MPG. Both MutLα or its ability to interact with MPG promote the generation of alkylation-induced abasic sites in cells, which contribute to the cytotoxicity of methyl methanesulfonate (MMS), an SN2 alkylating agent that does not produce O6meG. Our results provide new insight into the mechanism of alkylation chemoresistance and uncover an unappreciated cross-talk between MMR and BER.
SN - 0890-9369
SN - 1549-5477
ER -