Project description:To examine origin firing upon CDT1 overexpression, EdUseq-HU was performed in HCT116 cells with normal expression levels of CDT1 (OFF) and HCT116 cells with CDT1 overexpression (ON)
Project description:Colorectal adenomas are precursor lesions of colorectal cancers and represent clonal amplifications of single cells from colonic crypts. DNA methylation patterns specify cell-type identity during cellular differentiation and therefore provide novel opportunities for the molecular analysis of tumors. We have now analyzed DNA methylation patterns in colorectal adenomas and identified three biologically defined subclasses that describe different intestinal crypt differentiation stages. Importantly, colorectal carcinomas could be classified into the same methylation subtypes, reflecting their shared cell-types of origin with adenomas. Further data analysis also revealed significantly reduced overall survival for one of the subtypes. Our results establish a novel concept for understanding the methylation patterns observed in colorectal cancer and provide opportunities for tumor subclassification and patient stratification.
Project description:In mammals, it has long been hypothesized that DNA damage could induce DNA hypermethylation and contribute to carcinogenesis. However, the evidence that DNA damage is a cause of genome hypermethylation is still insufficient. Here, we demonstrated that, in plant, DNA damage can induce DNA hypermethylation in the context of symmetric CG, CHG as well as asymmetric CHH. Mechanically, DNA damage regulates the DREAM complex, to induce CG and CHG methylation. Moreover, DNA damage also utilizes the RdDM pathway to induce CHH hypermethylation. The hypermethylation sites of CG and CHG resulting from DNA damage tend to localize to gene body, and a large proportion of them are de nove generated. In contrast, the hypermethylation sites of CHH induced by DNA damage were mainly concentrated in the centromere and pre-centromere regions, and most of them are amplification of existing CHH methylation. Importantly, withdrawing the DNA damage or blocking the DNA damage response signal could fully abolish the CHH hypermethylation, partially rescue the CHG hypermethylation, but rarely recover the CG hypermethylation, indicating that DNA damage leaves symmetric DNA methylation as genetic imprinting. Collectively, our results suggest that DNA damage drives DNA methylation generation and evolution in plants.
Project description:In mammals, it has long been hypothesized that DNA damage could induce DNA hypermethylation and contribute to carcinogenesis. However, the evidence that DNA damage is a cause of genome hypermethylation is still insufficient. Here, we demonstrated that, in plant, DNA damage can induce DNA hypermethylation in the context of symmetric CG, CHG as well as asymmetric CHH. Mechanically, DNA damage regulates the DREAM complex, to induce CG and CHG methylation. Moreover, DNA damage also utilizes the RdDM pathway to induce CHH hypermethylation. The hypermethylation sites of CG and CHG resulting from DNA damage tend to localize to gene body, and a large proportion of them are de nove generated. In contrast, the hypermethylation sites of CHH induced by DNA damage were mainly concentrated in the centromere and pre-centromere regions, and most of them are amplification of existing CHH methylation. Importantly, withdrawing the DNA damage or blocking the DNA damage response signal could fully abolish the CHH hypermethylation, partially rescue the CHG hypermethylation, but rarely recover the CG hypermethylation, indicating that DNA damage leaves symmetric DNA methylation as genetic imprinting. Collectively, our results suggest that DNA damage drives DNA methylation generation and evolution in plants.