PARP4

PARP4 (poly(ADP-ribose) polymerase 4, also known as VPARP) is a member of the PARP family that catalyzes ADP-ribosylation and is predominantly associated with the vault ribonucleoprotein complex, linking it to cellular regulatory processes beyond canonical DNA damage sensing pathways^[1][2]. Unlike PARP1 and several other DNA-dependent PARP family members, PARP4 lacks the N-terminal DNA-binding domain that directly activates catalytic activity upon DNA damage, indicating a distinct regulatory mechanism that may depend on protein-protein interactions mediated by its extensive C-terminal region^[2][1]. Mechanistically, PARP family enzymes participate in ADP-ribosylation-dependent control of genomic stability, signal transduction, apoptosis, inflammatory regulation, and cellular stress responses, providing the broader biological context in which PARP4 functions are investigated^[3][4]. In disease-related studies, PARP4 has been implicated in cancer biology and has been reported to protect against lung adenocarcinoma progression through regulation of RNA splicing via interaction with hnRNPM^[1]. Experimental evidence further indicates that PARP4-deficient mice are viable and fertile under normal conditions but display increased susceptibility to chemically induced colon tumor formation, supporting a context-dependent role in tumor suppression^[1]. Compared with related PARP isoforms that are established therapeutic targets, the biological functions of PARP4 remain less completely defined, and no PARP4-selective inhibitors have achieved comparable research or clinical utility, making mechanistic studies of this isoform an active area of investigation^[3][4].