NAD+ regulates nucleotide metabolism and genomic DNA replication
Sebastian Howen Nesgaard Munk, Joanna Maria Merchut‐Maya, Alba Adelantado-Rubio, Arnaldur Hall, George D. Pappas, Giacomo Milletti, Myung‐Hee Lee, Lea G. Johnsen, Per Guldberg, Jiří Bártek, Apolinar Maya‐Mendoza
Abstract
Abstract The intricate orchestration of enzymatic activities involving nicotinamide adenine dinucleotide (NAD + ) is essential for maintaining metabolic homeostasis and preserving genomic integrity. As a co-enzyme, NAD + plays a key role in regulating metabolic pathways, such as glycolysis and Kreb’s cycle. ADP-ribosyltransferases (PARPs) and sirtuins rely on NAD + to mediate post-translational modifications of target proteins. The activation of PARP1 in response to DNA breaks leads to rapid depletion of cellular NAD + compromising cell viability. Therefore, the levels of NAD + must be tightly regulated. Here we show that exogenous NAD + , but not its precursors, has a direct effect on mitochondrial activity. Short-term incubation with NAD + boosts Kreb’s cycle and the electron transport chain and enhances pyrimidine biosynthesis. Extended incubation with NAD + results in depletion of pyrimidines, accumulation of purines, activation of the replication stress response and cell cycle arrest. Moreover, a combination of NAD + and 5-fluorouridine selectively kills cancer cells that rely on de novo pyrimidine synthesis. We propose an integrated model of how NAD + regulates nucleotide metabolism, with relevance to healthspan, ageing and cancer therapy.