“An End to a Means”: How DNA-End Structure Shapes the Double-Strand Break Repair Process

Abstract

Endogenously-arising DNA double-strand breaks (DSBs) rarely harbor canonical 5 ′ -phosphate, 3 ′ -hydroxyl moieties at the ends, which are, regardless of the pathway used, ultimately required for their repair. Cells are therefore endowed with a wide variety of enzymes that can deal with these chemical and structural variations and guarantee the formation of ligatable termini. An important distinction is whether the ends are directly "unblocked" by specific enzymatic activities without affecting the integrity of the DNA molecule and its sequence, or whether they are "processed" by unspecific nucleases that remove nucleotides from the termini. DNA end structure and configuration, therefore, shape the repair process, its requirements, and, importantly, its final outcome. Thus, the molecular mechanisms that coordinate and integrate the cellular response to blocked DSBs, although still largely unexplored, can be particularly relevant for maintaining genome integrity and avoiding malignant transformation and cancer.

Senataxin and RNase H2 act redundantly to suppress genome instability during class switch recombination

“…These two models of how persistent R loops impact CSR are not mutually exclusive, as DSB end structure directly affects repair protein binding affinity and which proteins are necessary for successful repair ( Chang et al, 2017 ; Serrano-Benítez et al, 2019 ; Symington, 2016 ). We propose that persistent R loops promote the formation of long (>6 bp) ssDNA tails, increasing the frequency of error-prone EJ at switch joins in Setx -/- , Rnaseh2b f/f , and Setx -/- Rnaseh2b f/f cells.…”

Senataxin and RNase H2 act redundantly to suppress genome instability during class switch recombination

“…These two models of how persistent R loops impact CSR are not mutually exclusive, as DSB end structure directly affects repair protein binding affinity and which proteins are necessary for successful repair (H. H. Y. Chang et al, 2017; Serrano-Benitez, Cortes-Ledesma, & Ruiz, 2019; Symington, 2016). We propose that persistent R loops promote the formation of long (> 6 bp) ssDNA tails, increasing the frequency of error-prone EJ at switch joins in Setx -/- , Rnaseh2b f/f , and Setx -/- Rnaseh2b f/f cells.…”

Discovery and Development of Novel DNA-PK Inhibitors by Targeting the unique Ku-DNA Interaction

“…Abundance and affinity would suggest that DNA-PK would likely be the first protein to arrive at a DSB, a point that has been debated, though recent evidence provides experimental evidence for the rapid association of DNA-PK with DNA ends in living cells (36). Biochemical and structural studies support the hypothesis that DNA-PK activation is driven by direct contact with DNA (37)(38)(39) and there is evidence that DNA structure and sequence play a unique and critical role in optimal DNA-PK activation (19;20). Previous work has shown that the Ku heterodimer is required for efficient NHEJ and functions as a scaffold for other NHEJ proteins to bind (40), including forming a critical interaction with DNA-PKcs.…”