title: Assays for DNA double-strand break repair by microhomology-based end-joining repair mechanisms.
abstract: DNA double stranded breaks (DSBs) are one of the most deleterious types of DNA lesions. The main pathways responsible for repairing these breaks in eukaryotic cells are homologous recombination (HR) and non-homologous end-joining (NHEJ). However, a third group of still poorly characterized DSB repair pathways, collectively termed microhomology-mediated end-joining (MMEJ), relies on short homologies for the end-joining process. Here, we constructed GFP reporter assays to characterize and distinguish MMEJ variant pathways, namely the simple MMEJ and the DNA synthesis-dependent (SD)-MMEJ mechanisms. Transfection of these assay vectors in Chinese hamster ovary (CHO) cells and characterization of the repaired DNA sequences indicated that while simple MMEJ is able to mediate relatively efficient DSB repair if longer microhomologies are present, the majority of DSBs were repaired using the highly error-prone SD-MMEJ pathway. To validate the involvement of DNA synthesis in the repair process, siRNA knock-down of different genes proposed to play a role in MMEJ were performed, revealing that the knock-down of DNA polymerase θ inhibited DNA end resection and repair through simple MMEJ, thus favoring the other repair pathway. Overall, we conclude that this approach provides a convenient assay to study MMEJ-related DNA repair pathways.
authors.affiliation: Institute of Biotechnology, University of Lausanne, and Center for Biotechnology UNIL-EPFL, Lausanne, Switzerland.
authors.forename: Kaja
authors.initials: K
authors.lastname: Kostyrko
authors.affiliation: Institute of Biotechnology, University of Lausanne, and Center for Biotechnology UNIL-EPFL, Lausanne, Switzerland nicolas.mermod@unil.ch.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mermod
mesh_terms: D000818:Animals; D001483:Base Sequence; D001681:Biological Assay; D016466:CHO Cells; D003412:Cricetulus; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair; D004259:DNA-Directed DNA Polymerase / Q000235:genetics* / Q000378:metabolism; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D059765:Homologous Recombination; D008969:Molecular Sequence Data; D010957:Plasmids / Q000737:chemistry / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection; D000097462:DNA Polymerase theta
chemical_list: D004247:DNA; D004259:DNA-Directed DNA Polymerase; D049452:Green Fluorescent Proteins; D034741:RNA, Small Interfering; D000097462:DNA Polymerase theta