ADP-ribosylation refers to a post-translational modification (PTM) involving the addition of ADP-ribose moieties to proteins. Whilst ADP-ribosylation is best known for its roles in DNA damage repair and cellular signalling, its involvement in chromatin regulation is an emerging area of research. One of the best-studied functions of ADP-ribosylation in chromatin regulation is its role in DNA damage repair. Poly (ADP-ribose) polymerases (PARPs) catalyse the addition of ADP-ribose units to proteins, including histones and other chromatin-associated proteins, in response to DNA damage. PARP1 is one of the first responders to DNA damage. When DNA strands break, PARP1 detects the damage and becomes activated. PARP1 binds to the sites of DNA damage, which can be single-strand breaks (SSBs) or double-strand breaks (DSBs). In the DNA damage response, PARP1 and PARP2 enzymes can ADP-ribosylate histones, particularly histone H1, histone H2B, and histone H3. PARylation leads to chromatin relaxation, making it more accessible for the DNA repair machinery to access DNA lesions. This modification also promotes the recruitment of DNA repair factors, such as XRCC1 and DNA ligase III, to the damaged sites. ADP-ribosylation of PARP1 itself also contributes to the formation of repair foci, where DNA repair proteins and chromatin modifiers are concentrated at DNA damage sites. This spatial organization facilitates efficient DNA repair processes. For example, PARP1 auto-modification, resulting in poly ADP-ribosylation of PARP1 itself, creates a scaffold for the recruitment of repair factors and chromatin modifiers. ADP-ribosylation can also regulate chromatin remodelling complexes. For example, ADP-ribosylation of CHD4 (Chromodomain Helicase DNA-binding Protein 4), a component of the nucleosome remodelling and deacetylase (NuRD) complex, disrupts its association with the NuRD complex, leading to changes in chromatin structure and gene expression. This mechanism has been implicated in the regulation of genes involved in DNA damage repair and cellular stress responses. ADP-ribosylation can also influence transcription by modulating the activity of transcription factors and cofactors that interact with chromatin. One example is the regulation of transcription factors such as p53, which plays an important role in the cellular response to DNA damage and stress. Upon activation, PARP1 catalyses the formation of PAR chains using NAD+ as a substrate. PARP1 undergoes auto-modification, leading to the synthesis of PAR chains on its own protein and other nearby proteins. PAR chains synthesized by activated PARP1 serve as binding sites for various proteins involved in the DNA damage response, including p53. The PAR chains on PARP1 and other proteins therefore act as a scaffold, facilitating recruitment to the site of DNA damage. PARylation of p53 may also disrupt the interaction between p53 and MDM2, preventing MDM2 from ubiquitinating p53 and targeting it for degradation. As a result, p53 levels increase in response to DNA damage. This ADP-ribosylation-mediated activation of p53 leads to changes in gene expression, including the upregulation of genes involved in cell cycle arrest and DNA repair. Thus, ADP-ribosylation plays multifaceted roles, being intimately involved in DNA damage repair but also involved in chromatin remodelling, transcriptional regulation, and the modulation of chromatin-associated proteins. We offer a large product catalogue of research reagents for investigating ADP ribosylation, including PARP1 antibodies, and PARP2 antibodies. Explore our full ADP ribosylation product range below and discover more, for less.