Cologne Seminars on Ageing "The Role of PARPs, NAD+, and Site-Specific ADP-ribosylation in the Control of Complex Biological Processes"

About Lee' s talk:

Nicotinamide adenine dinucleotide (NAD+) is a small molecule co-factor in metabolic redox reactions, as well as a signaling
molecule. We have found that NAD+ synthesis in mammalian cells is compartmentalized, with functionally distinct nuclear and cytosolic pools that support compartment-specific ADP-ribosylation by members of the poly(ADP-ribose) polymerase (PARP) family. For example, NAD+ synthesized in the nucleus of preadipocytes from NMN and ATP by nicotinamide mononucleotide adenylyl transferase-1 (NMNAT-1) plays a key role in inhibiting pro-adipogenic gene expression by PARP1, a nuclear enzyme that catalyzes the covalent attachment of poly(ADP-ribose) (PAR) chains on target proteins using NAD+ as a donor of ADP-ribose. A similar pathway is active in cancer cells as well. Likewise, NAD+ synthesized in the cytoplasm in ovarian cancer cells by NMNAT-2 plays a key role in controlling cytosolic mono(ADP-ribosyl)ation by mono(ADP-ribosyl) transferases (MARTs) and, ultimately, regulates protein translation. In mouse embryonic stem cells (mESCs), alterations in the spatial and temporal use of specific NAD+ biosynthetic pathways during differentiation lead to changes in the PARP1-mediated ADP-ribosylated (ADPRylated) proteome and mRNA isoform specialization through RNA splicing regulation. Collectively, our studies have elucidated functional links among compartment-specific NAD+ synthesis, PARP activity, ADP-ribosylation, and major cellular processes, including transcription, splicing, and translation. Our work has placed a particular emphasis on identifying, confirming, characterizing, and functionally analyzing specific sites of ADP-ribosylation in biologically relevant PARP substrate proteins in physiological processes in vivo.