Abstract
Background: Inherited defects in the base-excision repair gene MBD4 predispose individuals to adenomatous polyposis and colorectal cancer, which is characterized by an accumulation of C > T transitions resulting from spontaneous deamination of 5’-methylcytosine. Methods: Here, we have investigated the potential role of MBD4 in regulating DNA methylation levels using genome-wide transcriptome and methylome analyses. Additionally, we have elucidated its function through a series of in vitro experiments. Results: Here we show that the protein MBD4 is required for DNA methylation maintenance and G/T mismatch repair. Transcriptome and methylome analyses reveal a genome-wide hypomethylation of promoters, gene bodies and repetitive elements in the absence of MBD4 in vivo. Methylation mark loss is accompanied by a broad transcriptional derepression phenotype affecting promoters and retroelements with low methylated CpG density. MBD4 in vivo forms a complex with the mismatch repair proteins (MMR), which exhibits high bi-functional glycosylase/AP-lyase endonuclease specific activity towards methylated DNA substrates containing a G/T mismatch. Experiments using recombinant proteins reveal that the association of MBD4 with the MMR protein MLH1 is required for this activity. Conclusions: Our data identify MBD4 as an enzyme specifically designed to repair deaminated 5-methylcytosines and underscores its critical role in safeguarding against methylation damage. Furthermore, it illustrates how MBD4 functions in normal and pathological conditions.
Original language | American English |
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Pages | 301 |
Number of pages | 19 |
DOIs | |
State | Published - Nov 14 2023 |
Keywords
- DNA Methylation
- DNA Mismatch Repair
- DNA Repair
- Endodeoxyribonucleases/genetics
- Humans
- Recombinant Proteins/genetics
- Retroelements