Tankyrase Regulates Neurite Outgrowth through Poly(ADP-ribosyl)ation-Dependent Activation of β-Catenin Signaling

PARsylation-mediated ubiquitylation: lessons from rare hereditary disease Cherubism

Modification of proteins by ADP-ribose (PARsylation) is catalyzed by the poly(ADP-ribose) polymerase (PARP) family of enzymes exemplified by PARP1, which controls chromatin organization and DNA repair. Additionally, PARsylation induces ubiquitylation and proteasomal degradation of its substrates because PARsylation creates a recognition site for E3-ubiquitin ligase. The steady-state levels of the adaptor protein SH3-domain binding protein 2 (3BP2) is negatively regulated by tankyrase (PARP5), which coordinates ubiquitylation of 3BP2 by the E3-ligase ring finger protein 146 (RNF146). 3BP2 missense mutations uncouple 3BP2 from tankyrase-mediated negative regulation and cause Cherubism, an autosomal dominant autoinflammatory disorder associated with craniofacial dysmorphia. In this review, we summarize the diverse biological processes, including bone dynamics, metabolism, and Toll-like receptor (TLR) signaling controlled by tankyrase-mediated PARsylation of 3BP2, and highlight the therapeutic potential of this pathway.

Recent advances in cancer therapy using PARP inhibitors

When DNA repair is inadequate it increases the chances of the genome becoming unstable and it undergoes a malignant mutation. The deficiency of DNA repair PARP proteins may be leveraged for cancer therapy by increasing genomic instability and causing massive DNA damage in cancer cells. DNA repair components are under increased demand in cancer cells because of the continuous replication of DNA. The oncogenic loss of BRCA and an inefficient DNA repair led to cancer cells being dependent on particular DNA repair pathways, like the Poly (ADP-ribose) polymerase pathway. Breast cancer gene 1 and 2 plays a crucial role in DNA repair and genome integrity explaining how BRCA1 and BRCA2 mutations raise the menace of cancer. PARP inhibitors inhibit the base exclusion repair pathway, resulting in the buildup of unrepaired single strand breaks, which cause inflated replication forks in the S phase and subsequently the development of damaging double stranded breaks. Cells having BRCA mutations are unable to repair DNA breaks, leading to apoptosis and eventually death of cancer cells. Numerous indicators, such as a lack of homologous recombination and a high degree of replication pressure, indicate that this therapy will be very effective. Combining PARP inhibitors with chemotherapy, an immune checkpoint inhibitor, and a targeted drug is an effective strategy for combating PARP inhibitors resistance. Several PARP-based combination approaches are in preclinical and clinical development. Various clinical trials are successfully completed and some are undergoing to evaluate the efficacy of these molecules. This review will describe the current views and clinical updates on PARP inhibitors.

Functional roles of ADP-ribosylation writers, readers and erasers

ADP-ribosylation is a reversible post-translational modification (PTM) tightly regulated by the dynamic interplay between its writers, readers and erasers. As an intricate and versatile PTM, ADP-ribosylation plays critical roles in various physiological and pathological processes. In this review, we discuss the major players involved in the ADP-ribosylation cycle, which may facilitate the investigation of the ADP-ribosylation function and contribute to the understanding and treatment of ADP-ribosylation associated disease.