Nuclear One Carbon Metabolism

Folate metabolism is essential for providing one carbon intermediates needed to synthesize various biomolecules such as purines, thymidylate and methionine. In humans, deficiency in dietary folates or mutations in folate metabolic enzymes can lead to developmental defects, and antifolates are used therapeutically for the treatment of cancer. On the molecular level, the impairment of folate metabolism causes DNA damage, but the resulting metabolic and genetic dependencies have not been fully characterized. Based on our preliminary data, we aim to investigate the interplay between the core folate enzyme MTHFD1, adenosine metabolism, and ADP-ribosylation. We hypothesize that adenosine addition promotes the growth of MTHFD1 deficient cells by causing specific ADP-ribosylation dependent metabolic events that inactivate the key metabolic sensor AMPK. The objective of this project is to elucidate the molecular mechanism by which the understudied poly(ADP-ribose) polymerase PARP8 contributes to the growth-promoting effects of adenosine in folate deficient conditions. In a genome-wide genetic screen, we identified PARP8 as a top candidate regulating adenosine dependency in folate deficient cells. In this project, we will first characterize the fundamental functions of PARP8 including the role of its enzymatic activity, subcellular localization and interaction partners. We will then integrate this information with transcriptomic and metabolomic data to uncover how PARP8 influences biochemical signaling pathways and cellular energy sensing. Finally, we will assess the physiological role of PARP8 in the liver, where folate metabolism, PARP activity, and AMPK signaling are all known to be highly relevant to disease processes. Although folate metabolism and PARP enzymes have been widely studied due to their clinical relevance, this research has largely focused on established targets like DHFR and PARP1. In contrast, MTHFD1 and PARP8 are relatively understudied. Therefore, our study has the potential to uncover novel molecular mechanisms that deepen our understanding of human disease biology and provide novel therapeutic targets.