Replication fork protection and innate immune response

ABSTRACT Protection of stalled replication forks is crucial for cells to respond to replication stress and maintain genome stability. Recent research has provided strong evidences that genome instability can trigger inflammatory response when chromosomal or short stranded nuclear DNA are released into the cytoplasm and detected by

a cytosolic DNA sensing pathway, the cGAS-STING-dependent pathway. Emerging evidences indicate that DNA repair or replication fork processing in the replication stress response is connected with activation of the innate immune response. However, much remains unknown about the link between stalled replication fork

protection and innate immune response. In addition, the physiological consequence of replication stress- induced innate immune response in vivo remains to be defined. Our recent study reveals a role of Abro1 and FANCD2 in linking replication fork protection with restriction of innate immune response. We found that stalled

replication fork degradation induced by Abro1- or FANCD2-deficiency leads to accumulation of cytosolic single- stranded DNA (ssDNA) and activation of cGAS-STING-dependent innate immune signaling. Increased cytosolic ssDNA including ribosomal DNA (rDNA) binds to cGAS activating cGAS-dependent innate immune

signaling and secretion of proinflammatory cytokines/chemokines. In addition, Abro1 and FANCD2 limits replication stress-induced Processing bodies (P-bodies) formation and P-bodies are capable of modulating activation of the innate immune signaling upon replication stress. We propose to determine the underlying

mechanism by which replication fork protection limits the induction of innate immune response and define fork degradation-induced innate immune response in vivo. We will carry out the following specific aims: (1) to delineate stalled fork degradation-induced activation of innate immune signaling; (2) to determine the

involvement of P-bodies in stalled fork degradation-induced activation of innate immune signaling; (3) to determine the physiological effect of Abro1 deficiency-induced replication fork degradation associated secretory phenotype in vivo in mice. Overall, this project will provide novel insights into the link of replication

fork protection and innate immune response, contributing to establishing new possibilities for the treatment of inflammatory disorders and cancer in the future.