title: Endonuclease G initiates DNA rearrangements at the MLL breakpoint cluster upon replication stress.
abstract: MLL (myeloid/lymphoid or mixed-lineage leukemia) rearrangements are frequent in therapy-related and childhood acute leukemia, and are associated with poor prognosis. The majority of the rearrangements fall within a 7.3-kb MLL breakpoint cluster region (MLLbcr), particularly in a 0.4-kb hotspot at the intron11-exon12 boundary. The underlying mechanisms are poorly understood, though multiple pathways including early apoptotic signaling, accompanied by high-order DNA fragmentation, have been implicated. We introduced the MLLbcr hotspot in an EGFP-based recombination reporter system and demonstrated enhancement of both spontaneous and genotoxic treatment-induced DNA recombination by the MLLbcr in various human cell types. We identified Endonuclease G (EndoG), an apoptotic nuclease, as an essential factor for MLLbcr-specific DNA recombination after induction of replication stress. We provide evidence for replication stress-induced nuclear accumulation of EndoG, DNA binding by EndoG as well as cleavage of the chromosomal MLLbcr locus in a manner requiring EndoG. We demonstrate additional dependency of MLLbcr breakage on ATM signaling to histone H2B monoubiquitinase RNF20, involved in chromatin relaxation. Altogether our findings provide a novel mechanism underlying MLLbcr destabilization in the cells of origin of leukemogenesis, with replication stress-activated, EndoG-mediated cleavage at the MLLbcr, which may serve resolution of the stalled forks via recombination repair, however, also permits MLL rearrangements.
authors.affiliation: Gynecological Oncology, Department of Obstetrics and Gynecology, University of Ulm, Ulm, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Gole
authors.affiliation: Gynecological Oncology, Department of Obstetrics and Gynecology, University of Ulm, Ulm, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Baumann
authors.affiliation: Gynecological Oncology, Department of Obstetrics and Gynecology, University of Ulm, Ulm, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Mian
authors.affiliation: Gynecological Oncology, Department of Obstetrics and Gynecology, University of Ulm, Ulm, Germany.
authors.forename: C I
authors.initials: CI
authors.lastname: Ireno
authors.affiliation: Gynecological Oncology, Department of Obstetrics and Gynecology, University of Ulm, Ulm, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Wiesmüller
mesh_terms: D016590:Aphidicolin / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins / Q000502:physiology; D020169:Caspases / Q000502:physiology; D002478:Cells, Cultured; D053960:DNA Breaks; D004260:DNA Repair / Q000502:physiology; D004261:DNA Replication / Q000187:drug effects / Q000235:genetics*; D004706:Endodeoxyribonucleases / Q000502:physiology*; D006367:HeLa Cells; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics*; D006801:Humans; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011995:Recombination, Genetic / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics*; D014178:Translocation, Genetic / Q000187:drug effects
chemical_list: C497422:KMT2A protein, human; D019384:Nucleic Acid Synthesis Inhibitors; D051788:Myeloid-Lymphoid Leukemia Protein; D016590:Aphidicolin; D011495:Histone-Lysine N-Methyltransferase; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D004706:Endodeoxyribonucleases; C052391:endonuclease G; D020169:Caspases