MBD4 loss results in global reactivation of promoters and retroelements with low methylated CpG density.
Ontology highlight
ABSTRACT: 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. Despite its significance, this DNA repair pathway is still poorly understood. 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. The described data identify MBD4 as an enzyme specifically designed to repair deaminated 5-methylcytosines and illustrates how MBD4 functions in normal and pathological conditions.
Project description: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. Despite its significance, this DNA repair pathway is still poorly understood. 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. The described data identify MBD4 as an enzyme specifically designed to repair deaminated 5-methylcytosines and illustrates how MBD4 functions in normal and pathological conditions.
Project description: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. Despite its significance, this DNA repair pathway is still poorly understood. 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. The described data identify MBD4 as an enzyme specifically designed to repair deaminated 5-methylcytosines and illustrates how MBD4 functions in normal and pathological conditions.
Project description:AID-dependent U/G mismatches in S DNA are converted by BER and MMR DNA pathways into double-stranded breaks that are required for optimal CSR in activated B cells. Deficits in MMR proteins, MSH2, MLH1, and PMS2 result in lower CSR frequencies that are coupled with impaired DSB formation. MBD4 interacts with MLH1 and has been postulated to coordinate mismatch repair of U/G. Deletions of Mbd4 targeting the 5' end of the gene in mice do not affect CSR . However, Mbd4 transcription is complex, with the propensity to create alternative transcripts, including residual transcription leading to to truncated protein expression that complicates ananlysis in these mice. We describe a novel function of MBD4 housed in the C-terminus that is critical for DSB formation, which shares several characteristics with MMR . We conclude that the 3' end of the Mbd4 gene positively contributes to CSR and likely intersects the MMR pathway. 2 independent samples for each control and Mbd4 KO group
Project description:AID-dependent U/G mismatches in S DNA are converted by BER and MMR DNA pathways into double-stranded breaks that are required for optimal CSR in activated B cells. Deficits in MMR proteins, MSH2, MLH1, and PMS2 result in lower CSR frequencies that are coupled with impaired DSB formation. MBD4 interacts with MLH1 and has been postulated to coordinate mismatch repair of U/G. Deletions of Mbd4 targeting the 5' end of the gene in mice do not affect CSR . However, Mbd4 transcription is complex, with the propensity to create alternative transcripts, including residual transcription leading to to truncated protein expression that complicates ananlysis in these mice. We describe a novel function of MBD4 housed in the C-terminus that is critical for DSB formation, which shares several characteristics with MMR . We conclude that the 3' end of the Mbd4 gene positively contributes to CSR and likely intersects the MMR pathway.
Project description:Metastasis is the major cause of death in cancer patients, yet the genetic/epigenetic programs that drive metastasis are poorly understood. Here, we report a novel epigenetic reprogramming pathway that is required for breast cancer metastasis. Concerted differential DNA methylation is initiated by activation of the RON receptor tyrosine kinase by its ligand, macrophage stimulating protein (MSP). Through PI3K signaling, RON/MSP promotes expression of the G:T mismatch-specific thymine glycosylase MBD4. RON/MSP and MBD4-dependent aberrant DNA methylation results in misregulation of a specific set of genes. Knockdown of MBD4 reverses methylation at these specific loci, and blocks metastasis. We also show that the MBD4 glycosylase catalytic residue is required for RON/MSP-driven metastasis. Analysis of human breast cancers using a set of specific genes that are regulated by RON/MSP through MBD4-directed aberrant DNA methylation revealed that this epigenetic program is significantly associated with poor clinical outcome. Furthermore, inhibition of Ron kinase activity with a new pharmacological agent prevents activation of the RON/MBD4 pathway and blocks metastasis of patient-derived breast tumor grafts in vivo.
Project description:Metastasis is the major cause of death in cancer patients, yet the genetic/epigenetic programs that drive metastasis are poorly understood. Here, we report a novel epigenetic reprogramming pathway that is required for breast cancer metastasis. Concerted differential DNA methylation is initiated by activation of the RON receptor tyrosine kinase by its ligand, macrophage stimulating protein (MSP). Through PI3K signaling, RON/MSP promotes expression of the G:T mismatch-specific thymine glycosylase MBD4. RON/MSP and MBD4-dependent aberrant DNA methylation results in misregulation of a specific set of genes. Knockdown of MBD4 reverses methylation at these specific loci, and blocks metastasis. We also show that the MBD4 glycosylase catalytic residue is required for RON/MSP-driven metastasis. Analysis of human breast cancers using a set of specific genes that are regulated by RON/MSP through MBD4-directed aberrant DNA methylation revealed that this epigenetic program is significantly associated with poor clinical outcome. Furthermore, inhibition of Ron kinase activity with a new pharmacological agent prevents activation of the RON/MBD4 pathway and blocks metastasis of patient-derived breast tumor grafts in vivo.
Project description:The mismatch repair (MMR) family is a highly conserved group of proteins that function in correcting base-base and insertion-deletion mismatches generated during DNA replication. To systematically investigate the mismatch repair pathway, we conducted a proteomic analysis and identified MMR-associated protein complexes using a tandem-affinity purification coupled with mass spectrometry (TAP-MS) method. In total, we identified 262 high-confidence candidate interaction proteins (HCIPs).
Project description:The mismatch repair (MMR) family is a highly conserved group of proteins that function in correcting base-base and insertion-deletion mismatches generated during DNA replication. To systematically investigate the mismatch repair pathway, we conducted a proteomic analysis and identified MMR-associated protein complexes using a tandem-affinity purification coupled with mass spectrometry (TAP-MS) method. In total, we identified 262 high-confidence candidate interaction proteins (HCIPs).
Project description:Metastasis is the major cause of death in cancer patients, yet the genetic/epigenetic programs that drive metastasis are poorly understood. Here, we report a novel epigenetic reprogramming pathway that is required for breast cancer metastasis. Concerted differential DNA methylation is initiated by activation of the RON receptor tyrosine kinase by its ligand, macrophage stimulating protein (MSP). Through PI3K signaling, RON/MSP promotes expression of the G:T mismatch-specific thymine glycosylase MBD4. RON/MSP and MBD4-dependent aberrant DNA methylation results in misregulation of a specific set of genes. Knockdown of MBD4 reverses methylation at these specific loci, and blocks metastasis. We also show that the MBD4 glycosylase catalytic residue is required for RON/MSP-driven metastasis. Analysis of human breast cancers using a set of specific genes that are regulated by RON/MSP through MBD4-directed aberrant DNA methylation revealed that this epigenetic program is significantly associated with poor clinical outcome. Furthermore, inhibition of Ron kinase activity with a new pharmacological agent prevents activation of the RON/MBD4 pathway and blocks metastasis of patient-derived breast tumor grafts in vivo. Examination of 3 cell types.