Nuclear IMPDH2 controls the DNA damage response by modulating PARP1 activity
Lorena Espinar, Marta García‐Cao, Alisa Schmidt, Savvas Kourtis, Antoni Gañez Zapater, Carla Aranda-Vallejo, Ritobrata Ghose, Laura García–López, Ilir Sheraj, Natalia Pardo‐Lorente, Marina Bantulà, Laura Pascual‐Reguant, Evangelia Darai, María Guirola, Joan Montero, Sara Sdelci
Abstract
Nuclear metabolism and DNA damage response are intertwined processes, but the precise molecular links remain elusive. Here, we explore this crosstalk using triple-negative breast cancer (TNBC) as a model, a subtype often prone to DNA damage accumulation. We show that the de novo purine synthesis enzyme IMPDH2 is enriched on chromatin in TNBC compared to other subtypes. IMPDH2 chromatin localization is DNA damage dependent, and IMPDH2 repression leads to DNA damage accumulation. On chromatin, IMPDH2 interacts with and modulates PARP1 activity by controlling the nuclear availability of NAD+ to fine-tune the DNA damage response. However, when IMPDH2 is restricted to the nucleus, it depletes nuclear NAD+, leading to PARP1 cleavage and cell death. Our study identifies a non-canonical nuclear role for IMPDH2, acting as a convergence point of nuclear metabolism and DNA damage response. Metabolism plays an important role in response to DNA damage, however the underlying mechanisms are less clear. Here, the authors identify a non-canonical role of IMPDH2 wherein it is recruited to the chromatin following DNA damage and mediates PARP1-dependent DNA damage repair via the regulation of nuclear NAD+ levels.