Ligase 3–mediated end‐joining maintains genome stability of human embryonic stem cells

Abstract

Maintenance of human embryonic stem cells (hESCs) with stable genome is important for their future use in cell replacement therapy and disease modeling. Our understanding of the mechanisms maintaining genomic stability of hESC and our ability to modulate them is essential in preventing unwanted mutation accumulation during their in vitro cultivation. In this study, we show the DNA damage response mechanism in hESCs is composed of known, yet unlikely components. Clustered oxidative base damage is converted into DNA double‐strand breaks (DSBs) by base excision repair (BER) and then quickly repaired by ligase (Lig)3‐mediated end‐joining (EJ). If there is further induction of clustered oxidative base damage by irradiation, then BER‐mediated DSBs become essential in triggering the checkpoint response in hESCs. hESCs limit the mutagenic potential of Lig3–mediated EJ by DNA break end protection involving p53 binding protein 1 (53BP1), which results in fast and error‐free microhomology‐mediated repair and a low mutant frequency in hESCs. DSBs in hESCs are also repaired via homologous recombination (HR); however, DSB overload, together with massive end protection by 53BP1, triggers competition between error‐free HR and mutagenic nonhomologous EJ.—Kohutova, A., Raška, J., Kruta, M., Seneklova, M., Barta, T., Fojtik, P., Jurakova, T., Walter, C. A., Hampl, A., Dvorak, P., Rotrekl, V. Ligase 3–mediated end‐joining maintains genome stability of human embryonic stem cells. FASEB J. 33, 6778–6788 (2019). http://www.fasebj.org

Geomagnetic Shielding Enhances Radiation Resistance by Promoting DNA Repair Process in Human Bronchial Epithelial Cells

“…The concurrence of γH2AX and 53BP1 at the DSBs initiates an on-site DSB repair process, which can be detected by colocalized antibody binding [23,35]. The colocalization of 53BP1 and γH2AX foci in cells upon radiation has been found similar to the DSBs repair sites [24,36]. In particular, the phosphorylation of H2AX resulting from DNA damage may enhance the interaction between γH2AX and 53BP1, leading to an increased accumulation of 53BP1 foci at the sites of DSB in IR exposed cells.…”

A Paradigm Revolution or Just Better Resolution—Will Newly Emerging Superresolution Techniques Identify Chromatin Architecture as a Key Factor in Radiation-Induced DNA Damage and Repair Regulation?

“…Hence, NHEJ has historically been considered the dominant repair pathway in human cells, while broken DNA end resection is considered the critical factor for determining the pathway of repair and signaling [21]. However, notably, embryonic stem cells are essentially dependent on HR [22][23][24], and HR templated by homologous chromosomes is the predominant repair pathway throughout the cell cycle in these cells in mice [25]. The activity of NHEJ and HR thus evidently depends on additional factors uniformly affecting the cell nucleus (herein referred to as "global factors") ( Figure 1B).…”

“…The activity of NHEJ and HR thus evidently depends on additional factors uniformly affecting the cell nucleus (herein referred to as "global factors") ( Figure 1B). In addition to the cell cycle and cell type, as already mentioned [23,24], the degree of cell differentiation [26], corresponding chromatin condensation [27], genetic background [28][29][30] and physiological status, such as age [31] and hypoxia [32], are the most frequently reported determining factors. For instance, cell differentiation accompanied by chromatin condensation generally suppresses HR in favor of NHEJ but may even completely prevent DSB repair in extreme cases [27].…”

“…Among these factors, the type of incident radiation and the irradiation conditions should be discussed first. Because of its unique mode of action, (ir)radiation can be considered a global factor with a locally specific effect ( Figure 1C) [23]. The topology of DSBs in the cell nucleus, which crucially impacts the mechanism and efficiency of repair, is defined by the physical characteristics (especially the linear energy transfer; LET) of the radiation and irradiation conditions.…”

Bioinformatics and expression analysis of the Xeroderma Pigmentosum complementation group C (XPC) of Trypanosoma evansi in Trypanosoma cruzi cells

“…For instance, they do not present a recognizable ligase III, DBB2, XPA, CSA, and RPA3 genes (Passos-Silva et al, 2010). In humans' cells, severe consequences are observed if there is missfunction in ligase III (Kohutova et al, 2019), DDB2 (Yoon et al, 2005), XPA (Messaoud et al, 2012;Manandhar et al, 2017), CSA (D'errico et al, 2007) or RPA3 (Dai et al, 2017) protein. Further, T. cruzi, T. brucei and L. major have duplication of XPB gene (Passos-Silva et al, 2010).…”