CSB349L12 - DNA methylation We looked at HDACs HATs and...

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DNA methylation We looked at HDACs, HATs, and other histone protein modifications to effect chromatin. Now we are looking at direct modifications of DNA (at promoter for example), and how these changes effect gene expression. Methylating DNA tends to turn off gene expression at that particular locus. DNA methylation is CpG methylation carbon 5 of cytosine is the target of methylation, it is linked through backbone phosphodiester bonds to G. Depending on the type of species, there could be extensive methylation..there are hot spots of methylation. It also depends on the state of the cell. There is a concept of CpG islands (regions surrounding a gene where there is a high density of CpGs and where these can be differentially methylated to regulate gene expression). There is maintaince methylatino cell mehtylation patterns that can be gone from mother to daughter cells. There is also de novo mehtylation. There are three main enzymes: DNA methyltransferases. Dnmt1, Dnmt3a, and Dnmt3b. co-factor important for many processes in cell.
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The older version is in grey (has a particular pattern of mehtylation) which is inherited by the daughter cell. The new strand does not contain any mehtylation, but the cells machinery will use the new strand as a template of where to methylate (so there is a pattern preserved), this is important for the liver as the new daughter cells must preserve a particular pattern of methylation. A good method to ensure which cells will remain active or inactive. Dnmt1 only functions as a maintenance mehtylation enzyme whereas DnmT3a and b do it de novo. Can get screwed up in the context of disease. How the enzymes regulate methylation: knock out of all three enzymes separately. De novo methylation is normal but maintenance methylation is defective (for Dnmt1 knockout). In WT you should see increase in methylation b/c of de novo methylation.
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How do we detect methylation of DNA? Bisulfite sequencing is used to detect DNA methylation. Makes use of process where NA+ bisulphite can convert a cytosine to a uracil. If the cytosine is mehtylated, this chemical reaction cannot take place. IF
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