Project description:Benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon, is the major cause of lung cancer. It forms covalent DNA adducts after metabolic activation and induces mutations. We have developed a method capturing oligonucleotides carrying bulky base adducts, including UV-induced cyclobutane pyrimidine dimers (CPDs) and BaP diol epoxide-deoxyguanosine (BPDE-dG), which are removed from the genome by nucleotide excision repair. The isolated oligonucleotides are ligated to adaptors and after damage-specific immunoprecipitation the adaptor-ligated oligonucleotides are converted to dsDNA with an appropriate translesion DNA synthesis (TLS) polymerase followed by PCR amplification and next-generation sequencing (NGS) to generate genome-wide repair maps. We have named this method as translesion eXcision Repair-sequencing (tXR-seq). In contrast to our previously described XR-seq method, the tXR-seq does not depend on repair/removal of the damage in the excised oligonucleotides and hence it is applicable to essentially all DNA damages processed by nucleotide excision repair. Here, we present the excision repair maps for CPDs and BPDE-dG adducts generated by tXR-Seq for the human genome. Additionally, we observe novel sequence specificity of BPDE-dG excision repair by using tXR-seq.
2017-06-12 | GSE97675 | GEO
Project description:Studies of Pol V-mediated translesion synthesis
Project description:DNA polymerase (pol) is a Y-family translesion synthesis polymerase that plays a key role in the cellular tolerance toward UV irradiation-induced DNA damage. Here, we identified, for the first time, the phosphorylation of serine 687 (S687), which islocated in the highly conserved nuclear localization signal (NLS) region of human pol and is mediated by cyclin-dependent kinase 2 (CDK2). We also showed that this phosphorylation is stimulated in human cells upon UV light exposure and results in diminished interaction of pol with proliferating cell nuclear antigen (PCNA). Furthermore, we demonstrated that the phosphorylation of S687 in polconfers cellular protection fromUV irradiation and increases the efficiency in replication across a site-specifically incorporated cyclobutane pyrimidine dimer in human cells. Based on these results, we proposed a mechanistic model where S687 phosphorylation functions in the reverse polymerase switching step of translesion synthesis: The phosphorylation brings negative charges to the NLS of pol, which facilitates its departure from PCNA, thereby resetting the replication fork for highly accurate and processive DNA replication. Thus, our study, together with previous findings, supported that the post-translational modifications of NLS of pol played a dual role in polymerase switching, where K682 deubiquitination promotes the recruitment of pol to PCNA immediately prior to lesion bypass and S687 phosphorylation stimulates its departure from the replication fork immediately after lesion bypass.