Oncogenic YAP sensitizes cells to CHK1 inhibition via CDK4/6 driven G1 acceleration

Replication stress is a driver of genomic instability, contributing to carcinogenesis by causing DNA damage and mutations. While YAP, the downstream co-activator of the Hippo signaling pathway, plays a crucial role in regulating cell growth and differentiation, it is unclear whether it generates replication stress exploitable for therapy. Here, we report that oncogenic YAP shortens the G1 phase through increased CDK4/6 activity, leading to early S-phase entry. This causes origin under-licensing, an overall reduced rate of DNA replication, and, untypically, an accelerated speed of individual replication forks. CHK1 inhibition in cells expressing oncogenic YAP results in DNA damage during S-phase, which is not due to premature CDK1 activation or mitotic entry. Sensitivity to CHK1 inhibition depends on the YAP-TEAD interaction and involves a global increase in transcription and an increase in transcription-replication conflicts (TRCs). Replication stress from oncogenic YAP can be mitigated by restoring G1 length through partial CDK4/6 inhibition or by reducing YAP-induced hypertranscription. Our findings suggest a potential therapeutic strategy for targeting YAP-dependent cancers by exploiting their vulnerability to replication stress. MapR of MCF10A cells with doxycycline inducible YAP5SA to detect R-loops. Control MCF10A cells and YAP5SA expressing cells were treated with the CHK1 inhibitor prexasertib. As a positive control for MapR, MCF10A cells were treated with the BRD4 inhibitor JQ1.