Cytosolic DNA and intracellular Ca²⁺: Maintaining genome stability during replication stress

Maintaining genome stability during DNA replication is a critical cellular challenge. Various surveillance and repair mechanisms have evolved to cope with replication stress, which can be caused by environmental insults, metabolic byproducts, complex DNA structures in the genome, and replication-transcription conflicts. This perspective highlights a newly identified cytosolic DNA/Ca²⁺-dependent signaling pathway that plays a crucial role in protecting stalled replication forks. The pathway involves cytosolic DNA generation and its sensing by the cGAS-cGAMP-STING axis, TRPV2-mediated Ca²⁺ release from the ER, and activation of a CaMKK2-AMPK protein phosphorylation cascade that suppresses the EXO1 nuclease, thereby preventing aberrant fork processing and preserving chromosomal integrity. Separate from the ATR/Chk1 checkpoint, this cytoDNA/Ca²⁺-dependent pathway represents a non-redundant mechanism for genome maintenance, with potentially important implications for cancer formation and its treatment. Moreover, the intersection of this pathway with other signaling networks also enables coordinated regulation of genome maintenance, immune response, autophagy, and cellular senescence.