SP14 Modulation of PARP1 enzymatic activity in genotoxic response and tissue homeostasis

Projekt leader: Zhao-Qi Wang

Background and previous work
Poly(ADP-ribosyl)ation (PARylation), catalysed by poly(ADP-ribose) polymerase 1 (PARP1), is the most rapid posttranslational modification in responses to genotoxic insults, particularly single- stranded DNA (SSBs) and replication stress. Accurate modulation of PARylation and the PARP1 activity are important in DNA repair, transcription, chromatin modulation, cell death, inflammation and ageing. Poly(ADP-ribose) (PAR) polymers is a moiety with a highly negative charge and has been hypothesised to function as a signal to other cellular targets. Our lab previously generated several mouse mutants, which either harbour various level of PARylation capacity or lack the PARP1 protein. We recently showed that a direct interaction of PAR and Chk1 regulates the intra-S phase checkpoint, highlighting interplay of PAR metabolism and cell cycle control. However, due to its multiple interdependent functions of PARP1, it remains enigmatic how its enzymatic activity and its product PAR are involved in these processes.

Specific aims and working programme
To study whether the PARP1 enzymatic activity can be separated from the function of the PARP1 protein as a scaffold protein in PARylation-mediated biological processes, we will generate an enzyme-dead mouse mutant (PARP1E988K), in which the glutamic acid (E) will be changed to lysine (K) in the codon 988 of PARP1. We will investigate (1) general development, tissue homeostasis and ageing-related pathologies; (2) the DNA damage response and the repair capacity of PARP1E988K cells in dose-dependent manner; (3) cell cycle checkpoint activation and cell death in mutant cells and tissues; (4) hormetic response to genotoxic response in mouse and cellular models. Moreover, this mouse model will be used to investigate the role of PARP1 during septic shock with or without preconditioning and the CNS inflammatory response.