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Mao C, Li S, Che J, Liu D, Mao X, Rao H. The ubiquitin ligase UBR4 and the deubiquitylase USP5 modulate the stability of DNA mismatch repair protein MLH1. J Biol Chem 2024:107592. [PMID: 39032648 DOI: 10.1016/j.jbc.2024.107592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 06/29/2024] [Accepted: 07/10/2024] [Indexed: 07/23/2024] Open
Abstract
MLH1 plays a critical role in DNA mismatch repair and genome maintenance. MLH1 deficiency promotes cancer development and progression, but the mechanism underlying MLH1 regulation remains enigmatic. In this study, we demonstrate that MLH1 protein is degraded by the ubiquitin-proteasome system and have identified vital cis-elements and trans-factors involved in MLH1 turnover. We found that the region encompassing the amino acids 516-650 is crucial for MLH1 degradation. The mismatch repair protein PMS2 may shield MLH1 from degradation as it bind to the MLH1 segment key to its turnover. Furthermore, we have identified the E3 ubiquitin ligase UBR4 and the deubiquitylase USP5, which oppositely modulate MLH1 stability. In consistence, UBR4 or USP5 deficiency affects the cellular response to nucleotide analog 6-TG, supporting their roles in regulating mismatch repair. Our study has revealed important insights into the regulatory mechanisms underlying MLH1 proteolysis, critical to DNA mismatch repair related diseases.
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Affiliation(s)
- Chenyu Mao
- Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Shenzhen, China, 518055
| | - Siqi Li
- Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Shenzhen, China, 518055
| | - Jun Che
- Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Shenzhen, China, 518055
| | - Dongzhou Liu
- Department of Rheumatology and Immunology, Shenzhen People's Hospital; The First Affiliated Hospital, Southern University of Science and Technology, Shenzhen, Guangdong, China, 518055
| | - Xinliang Mao
- Guangdong Provincial Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, Guangdong, China, 511436.
| | - Hai Rao
- Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Shenzhen, China, 518055; Key University Laboratory of Metabolism and Health of Guangdong, Southern University of Science and Technology, Shenzhen, China, 518055.
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Pelletier D, Rath A, Sabbaghian N, Pelmus M, Hudon C, Jacob K, Witowski L, Saskin A, Heinen CD, Foulkes WD. Functional and phenotypic consequences of an unusual inversion in MSH2. Fam Cancer 2024; 23:1-7. [PMID: 37957483 DOI: 10.1007/s10689-023-00350-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 10/27/2023] [Indexed: 11/15/2023]
Abstract
Lynch syndrome is an autosomal dominant disorder that usually results from a pathogenic germline variant in one of four genes (MSH2, MSH6, MLH1, PMS2) involved in DNA mismatch repair. Carriers of such variants are at risk of developing numerous cancers during adulthood. Here we report on a family suspected of having Lynch syndrome due to a history of endometrial adenocarcinoma, ovarian clear cell carcinoma, and adenocarcinoma of the duodenum in whom we identified a germline 29 nucleotide in-frame inversion in exon 3 of MSH2. We further show that this variant is almost completely absent at the protein level, and that the associated cancers have complete loss of MSH2 and MSH6 expression by immunohistochemistry. Functional investigation of this inversion in a laboratory setting revealed a resultant abnormal protein function. Thus, we have identified an unusual, small germline inversion in a mismatch repair gene that does not lead to a premature stop codon yet appears likely to be causal for the observed cancers.
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Affiliation(s)
- Dylan Pelletier
- Department of Human Genetics, Medicine, McGill University, Montreal, QC, Canada
- Cancer Axis, Lady Davis Institute, Jewish General Hospital, Montreal, QC, Canada
- Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Abhijit Rath
- Center for Molecular Oncology, UConn Health, Farmington, CT, USA
| | - Nelly Sabbaghian
- Department of Human Genetics, Medicine, McGill University, Montreal, QC, Canada
- Cancer Axis, Lady Davis Institute, Jewish General Hospital, Montreal, QC, Canada
| | - Manuela Pelmus
- Department of Pathology, Medicine, McGill University, Montreal, QC, Canada
| | - Catherine Hudon
- Department of Human Genetics, Medicine, McGill University, Montreal, QC, Canada
- Division of Medical Genetics, Dept of Specialized Medicine, Jewish General Hospital, Montreal, QC, Canada
| | - Karine Jacob
- Service de Médecine Génique, Centre Hospitalier de l'Université de Montréal, Montréal, QC, Canada
| | - Leora Witowski
- Department of Human Genetics, Medicine, McGill University, Montreal, QC, Canada
| | - Avi Saskin
- Service de Médecine Génique, Centre Hospitalier de l'Université de Montréal, Montréal, QC, Canada
| | | | - William D Foulkes
- Department of Human Genetics, Medicine, McGill University, Montreal, QC, Canada.
- Cancer Axis, Lady Davis Institute, Jewish General Hospital, Montreal, QC, Canada.
- Division of Medical Genetics, Dept of Specialized Medicine, Jewish General Hospital, Montreal, QC, Canada.
- Cancer Research Program, Research Institute of the McGill University Health Center, Montreal, QC, Canada.
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Christowitz C, Olivier DW, Schneider JW, Kotze MJ, Engelbrecht AM. Incorporating functional genomics into the pathology-supported genetic testing framework implemented in South Africa: A future view of precision medicine for breast carcinomas. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2024; 793:108492. [PMID: 38631437 DOI: 10.1016/j.mrrev.2024.108492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 02/25/2024] [Accepted: 04/11/2024] [Indexed: 04/19/2024]
Abstract
A pathology-supported genetic testing (PSGT) framework was established in South Africa to improve access to precision medicine for patients with breast carcinomas. Nevertheless, the frequent identification of variants of uncertain significance (VUSs) with the use of genome-scale next-generation sequencing has created a bottleneck in the return of results to patients. This review highlights the importance of incorporating functional genomics into the PSGT framework as a proposed initiative. Here, we explore various model systems and experimental methods available for conducting functional studies in South Africa to enhance both variant classification and clinical interpretation. We emphasize the distinct advantages of using in vitro, in vivo, and translational ex vivo models to improve the effectiveness of precision oncology. Moreover, we highlight the relevance of methodologies such as protein modelling and structural bioinformatics, multi-omics, metabolic activity assays, flow cytometry, cell migration and invasion assays, tube-formation assays, multiplex assays of variant effect, and database mining and machine learning models. The selection of the appropriate experimental approach largely depends on the molecular mechanism of the gene under investigation and the predicted functional effect of the VUS. However, before making final decisions regarding the pathogenicity of VUSs, it is essential to assess the functional evidence and clinical outcomes under current variant interpretation guidelines. The inclusion of a functional genomics infrastructure within the PSGT framework will significantly advance the reclassification of VUSs and enhance the precision medicine pipeline for patients with breast carcinomas in South Africa.
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Affiliation(s)
- Claudia Christowitz
- Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Stellenbosch 7600, South Africa.
| | - Daniel W Olivier
- Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Stellenbosch 7600, South Africa; Division of Chemical Pathology, Department of Pathology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7505, South Africa
| | - Johann W Schneider
- Division of Anatomical Pathology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7505, South Africa; National Health Laboratory Service, Tygerberg Hospital, Cape Town 7505, South Africa
| | - Maritha J Kotze
- Division of Chemical Pathology, Department of Pathology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7505, South Africa; National Health Laboratory Service, Tygerberg Hospital, Cape Town 7505, South Africa
| | - Anna-Mart Engelbrecht
- Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Stellenbosch 7600, South Africa; Department of Global Health, African Cancer Institute, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7505, South Africa
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Madden-Hennessey K, Gupta D, Radecki AA, Guild C, Rath A, Heinen CD. Loss of mismatch repair promotes a direct selective advantage in human stem cells. Stem Cell Reports 2022; 17:2661-2673. [PMID: 36368329 PMCID: PMC9768573 DOI: 10.1016/j.stemcr.2022.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 10/11/2022] [Accepted: 10/12/2022] [Indexed: 11/11/2022] Open
Abstract
Lynch syndrome (LS) is the most common hereditary form of colon cancer, resulting from a germline mutation in a DNA mismatch repair (MMR) gene. Loss of MMR in cells establishes a mutator phenotype, which may underlie its link to cancer. Acquired downstream mutations that provide the cell a selective advantage would contribute to tumorigenesis. It is unclear, however, whether loss of MMR has other consequences that would directly result in a selective advantage. We found that knockout of the MMR gene MSH2 results in an immediate survival advantage in human stem cells grown under standard cell culture conditions. This advantage results, in part, from an MMR-dependent response to oxidative stress. We also found that loss of MMR gives rise to enhanced formation and growth of human colonic organoids. These results suggest that loss of MMR may affect cells in ways beyond just increasing mutation frequency that could influence tumorigenesis.
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Affiliation(s)
| | - Dipika Gupta
- Center for Molecular Oncology, UConn Health, Farmington, CT 06030-3101, USA
| | | | - Caroline Guild
- Center for Molecular Oncology, UConn Health, Farmington, CT 06030-3101, USA
| | - Abhijit Rath
- Center for Molecular Oncology, UConn Health, Farmington, CT 06030-3101, USA
| | - Christopher D. Heinen
- Center for Molecular Oncology, UConn Health, Farmington, CT 06030-3101, USA,Corresponding author
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