Detection of 5mC and 5hmC in DNA templates generated by PCR using modified dCTPs by linear PCR using KTq DNA polymerase variant RIV A8
Ontology highlight
ABSTRACT: We have engineered the thermostable KlenTaq DNA polymerase variant called RIV A8 that produces error signatures specific for 5-methylcytosine (5mC) and 5-hydroxycytosine (5hmC) without prior chemical treatment of the DNA samples. These signatures are amplified during DNA amplicon library preparation and are detected by NGS. This method was applied to distinguish C from 5mC and C from 5hmC in DNA templates generated by PCR using modified dCTPs (unmodified by using dCTP, methylated by using d5mCTP, hydroxymethylated by using d5hmCTP).
Project description:We have engineered thermostable KlenTaq DNA polymerase variants called RIII H20, RIV A8 and RIV D15 that produce error signatures specific for 5-methylcytosine (5mC) without prior chemical treatment of the DNA samples. These signatures are amplified during DNA amplicon library preparation and are detected by NGS. This method was applied to distinguish C from 5mC in DNA templates generated by PCR (unmodified and methylated using the CpG Methyltransferase (M.SssI)). Finally, RIV A8 was used to detect 5mC in HeLa human genomic DNA (native methylation and supplementary methylated using the CpG Methyltransferase (M.SssI))
Project description:Detection of 5mC and 5hmC in DNA templates generated by PCR using modified dCTPs by linear PCR using KTq DNA polymerase variant RIV A8
Project description:DNA methylation (5mC) plays important roles in epigenetic regulation of genome function, and recently the TET1-3 hydroxylases have been found to oxidize 5mC to hydroxymethylcytosine (5hmC), formylcytosine (5fC), and carboxylcytosine (5caC) in DNA. These derivatives have a role in demethylation of DNA but in addition may have epigenetic signaling functions in their own right. A recent study identified proteins with preferential binding to 5-methylcytosine (5mC) and its oxidized forms where readers for 5mC and 5hmC (5-hydroxymethylcytosine) showed little overlap while further oxidation forms enriched for repair proteins and transcription regulators. We extend this study by using promoter sequences as baits and compare protein binding patterns to unmodified or modified cytosine containing DNA using mouse embryonic stem cell (mESCs) extracts. The dataset contains 3 biological replicates each of mouse ES cell nuclear proteins binding to Pax6 and FGF15 promoter sequences containing different modified forms of cytosine. Data analysis: Mass spectrometric data were processed using Proteome Discoverer v1.3 and searched against a mammalian entries in Uniprot 2011.09 using Mascot v2.3 with the following parameters: Enzyme - trypsin; max 1 missed cleavage; Precursor Mass Tolerance - 10 ppm; Fragment Mass Tolerance - 0.6 Da; Dynamic Modification - Oxidation (M); Static Modification - Carbamidomethyl at C.
Project description:5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) are modified versions of cytosine in DNA with roles in regulating gene expression. Using whole genomic DNA from mouse cerebellum, we benchmark 5mC and 5hmC detection by Oxford Nanopore Technologies sequencing against other standard techniques. In addition, we assess the ability of duplex base-calling to study strand asymmetric modification. Nanopore detection of 5mC and 5hmC is accurate relative to compared techniques and opens new means of studying these modifications. Strand asymmetric modification is widespread across the genome but reduced at imprinting control regions and CTCF binding sites in mouse cerebellum. Here we demonstrate the unique ability of nanopore sequencing to improve the resolution and detail of cytosine modification mapping.
Project description:Cytosine DNA bases can be methylated by DNA methyltransferases and subsequently oxidized by TET proteins. The resulting 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC) are considered demethylation intermediates as well as stable epigenetic marks. To dissect the contribution of these cytosine modifying enzymes, we generated combinations of Tet knockout (KO) embryonic stem cells (ESCs) and systematically measured protein and DNA modification levels at the transition from naive to primed pluripotency. Whereas the increase of genomic 5-methylcytosine (5mC) levels during exit from pluripotency correlated with an upregulation of the de novo DNA methyltransferases DNMT3A and DNMT3B, the subsequent oxidation steps turned out to be far more complex. The strong increase of oxidized cytosine bases (5hmC, 5fC, and 5caC) was accompanied by a drop in TET2 levels, yet the analysis of KO cells suggested that TET2 is responsible for most 5fC formation. The comparison of modified cytosine and enzyme levels in Tet KO cells revealed distinct and differentiation-dependent contributions of TET1 and TET2 to 5hmC and 5fC formation arguing against a processive mechanism of 5mC oxidation. The apparent independent steps of 5hmC and 5fC formation suggest yet to be identified mechanisms regulating TET activity and may constitute another layer of epigenetic regulation.