ATM specifically mediates repair of double-strand breaks with blocked DNA ends

Abstract

Ataxia telangiectasia is caused by mutations in ATM and represents a paradigm for cancer predisposition and neurodegenerative syndromes linked to deficiencies in the DNA-damage response. The role of ATM as a key regulator of signalling following DNA double-strand breaks (DSBs) has been dissected in extraordinary detail, but the impact of this process on DSB repair still remains controversial. Here we develop novel genetic and molecular tools to modify the structure of DSB ends and demonstrate that ATM is indeed required for efficient and accurate DSB repair, preventing cell death and genome instability, but exclusively when the ends are irreversibly blocked. We therefore identify the nature of ATM involvement in DSB repair, presenting blocked DNA ends as a possible pathogenic trigger of ataxia telangiectasia and related disorders.

ZATT (ZNF451)–mediated resolution of topoisomerase 2 DNA-protein cross-links

“…This prompted us to evaluate the untested link between the proteasome and TDP2 in repair of poisoned TOP2cc by monitoring the resolution of phospho-histone H2AX (γH2AX) foci following etoposide treatment. As reported previously, Tdp2 knockout ( Tdp2 −/− ) mouse embryonic fibroblasts (MEFs) display delayed resolution of etoposide-induced γH2AX foci compared to Tdp2 +/+ cells (11), and this was severely impaired by proteasome inhibition with MG132 (Fig. 1C, S1F).…”

Homology-Directed Repair and the Role of BRCA1, BRCA2, and Related Proteins in Genome Integrity and Cancer

“…Loss of ATM reduces HDR in some contexts but not in others (Alvarez-Quilon et al 2014, Beucher et al 2009, Chen et al 2017, Kass et al 2013, Morrison et al 2000, Rass et al 2013, White et al 2010), possibly due in part to redundancy of substrate phosphorylation by other PI3K-related kinase family members, namely ATR and DNA-PKcs (Tomimatsu et al 2009). However, several ATM targets have been clearly implicated in HDR.…”

An optimized TALEN application for mutagenesis and screening inDrosophila melanogaster

“…We argue the widespread stress response from unfixed DNA damage from many cells in the targeted embryo leads to the lethality we observe. 60 Comparing the white and ebony targeting CRISPR experiments in maternal and zygotic Lig4 null embryos, we demonstrate that more efficient targeting leads to significant less chance of the embryo to fix the breaks and continue its development. Thus Lig4 null embryo lethality is truly a very sensitive assay to estimate the efficiency of gene targeting.…”