A genome-wide screen reveals Ints7 deficiency activates endogenous retrovirus MERVL, accompanied by anastasis of embryonic stem cells [E14TG2a]

The murine endogenous retrovirus MERVL is closely associated with the developmental potential of totipotency, manifesting dynamic and reversible activation within a small population of in vitro-cultured mouse embryonic stem cells (mESCs). While numerous regulators have been identified to influence the on and off switches of MERVL, how its activation is linked to the cellular decision-making of mESCs remains poorly understood. In this study, our genome-wide knockout screen uncovered an intimate relationship between MERVL activation and DNA damage response pathways. Specifically, we found that deficiency of Ints7, a backbone subunit of the Integrator complex, resulted in increased DNA damage, stabilization of p53, and hence transcriptional activation of MERVL. Moreover, we revealed that MERVL activation upon Ints7 knockdown was frequently accompanied by the activation of caspase 3. Intriguingly, a proportion of the caspase-activated mESCs were able to switch on MERVL meanwhile circumvent apoptosis and evade cell death, resembling a process known as anastasis. Altogether, our study highlights an association between MERVL activation and the p53-dependent cell fate plasticity in response to DNA damage, suggesting that limited caspase activation can alter developmental potential of stem cells.