PARP

PARP-1 (poly(ADP-ribose) polymerase 1) is a nuclear ADP-ribosyl transferase that functions as an early sensor of DNA strand breaks and coordinates cellular responses to genomic damage through poly(ADP-ribosyl)ation-dependent signaling^[1][2]. Mechanistically, PARP-1 participates in multiple DNA repair pathways, including base excision repair (BER), homologous recombination (HR), and non-homologous end joining (NHEJ), where it promotes chromatin remodeling and recruitment of repair factors to damaged DNA sites^[1][2][3]. Through these activities, PARP-1 contributes to genome surveillance and maintenance of genomic stability, processes that are frequently disrupted during tumor development^[1][2]. In cancer biology, dysregulated PARP-1 function has been associated with disease progression, and inhibition of PARP-mediated DNA repair can reduce tumor cell viability by exploiting defects in homologous recombination repair pathways^[1][4]. Compared with the closely related isoform PARP-2, PARP-1 is the dominant mediator of single-strand break repair, whereas PARP-2 shares DNA repair functions but also displays distinct roles in biological processes including inflammation, metabolism, oxidative stress responses, and cancer progression^[3][5]. This functional distinction is important for understanding isoform-specific biology and for designing selective therapeutic strategies^[5]. For experimental and translational applications, PARP inhibitors have become widely used tools to interrogate DNA damage responses and to target tumors with DNA repair deficiencies, particularly those characterized by homologous recombination defects^[1][4].