TCAF1 Promotes TRPV2-mediated Ca2+ Release in Response to Cytosolic DNA to Protect Stressed Replication Forks

The protection of the replication fork structure under stress conditions is essential for genome maintenance and cancer prevention. A key signaling pathway for fork protection involves TRPV2-mediated Ca2+ release from the ER, which is triggered after the generation of cytosolic DNA and the activation of cGAS/STING. The resulting CaMKK2/AMPK activation and subsequent Exo1 phosphorylation prevent aberrant fork processing, thereby ensuring genome stability. However, it remains poorly understood how the TRPV2 channel is activated by the presence of cytosolic DNA. Here we show that the TRPM8 channel-associated factor 1 (TCAF1) plays a key role in promoting TRPV2-mediated Ca2+ release under replication stress or other conditions that activate cGAS/STING. Mechanistically, TCAF1 promotes Ca2+ release by facilitating the dissociation of STING from TRPV2, thereby relieving TRPV2 repression. Consistent with this function, TCAF1 is required for fork protection, chromosomal stability and cell survival after replication stress. To investigate how STING-TRPV2 dissociation occurs under replication stress, we carried out a genome-wide CRISPR/Cas9 screen in an effort to identify additional factors that regulate TRPV2 in the Ca2+-dependent pathway required for fork protection and cell survival in the presence of replication stress.