Investigating the Role of Poly (ADP-Ribose) Polymerase 1 (PARP1) in the Prevention of R-Loop-Mediated Genomic Instability
Abstract
PARP1 is a DNA-dependent diphtheria toxin-like ADP ribosyltransferase (ARTD) with ADP-ribosylation activity that is triggered by single- and double-stranded DNA breaks (SSBs and DSBs, respectively) to facilitate the DNA damage response (DDR) and repair of the lesions. Upon induction of DNA damage, PARP1 localizes to and binds the damaged DNA before utilizing NAD+ to synthesize long, branched chains of poly (ADP-ribose) (PAR) onto itself or other protein targets that facilitate the recruitment of downstream DNA repair proteins to repair the breaks. While SSBs and DSBs are the classical substrates of PARP1 that were first characterized upon discovery of the enzyme, PARP1 has since been demonstrated to be able to recognize and bind a wide variety of nucleic acid structures beyond DNA breaks, including RNA, DNA cruciforms and hairpins, and G-quadruplexes (G4). PARP1 was recently identified as a component of the R-loop-associated protein interactome, suggesting a potential role for PARP1 in the resolution of these structures. R-loops are three-stranded nucleic acid structures that consist of a DNA:RNA hybrid and a displaced non-template DNA strand that are mainly formed during transcription. R-loops play physiological roles in several crucial cellular processes but can also serve as a source of DNA damage and promote genomic instability if persistent, unresolved, or formed in an unscheduled manner. We hypothesized that PARP1 is able to recognize and bind R-loop structures, and that binding to R-loops triggers its catalytic activity. Here, we demonstrate that PARP1 binds R-loops in vitro and associates with R-loop formation sites in cells, which triggers its ADP-ribosylation activity. Conversely, we show that the inhibition or genetic depletion of PARP1 causes an accumulation of unresolved R-loops that promotes genomic instability. Our study demonstrates that PARP1 is a novel sensor of R-loop structures and highlights PARP1 as a suppressor of R-loop-associated genomic instability.
Subject Area
Biochemistry|Cellular biology|Molecular biology|Genetics
Recommended Citation
Laspata, Natalie, "Investigating the Role of Poly (ADP-Ribose) Polymerase 1 (PARP1) in the Prevention of R-Loop-Mediated Genomic Instability" (2023). ProQuest ETD Collection - Thomas Jefferson University. AAI30813349.
https://jdc.jefferson.edu/dissertations/AAI30813349
