PARP1-mediated PARylation of TEAD4 stabilizes the YAP1-TEAD4 complex and promotes growth and immune evasion in breast cancer cells

The transcriptional coactivator YAP1 regulates numerous biological processes, including organ size control and tissue homeostasis. Although its hyperactivity promotes tumor development and progression, YAP1 itself is not yet druggable. Here, we found that the poly(ADP-ribose) polymerase PARP1 promoted the transcriptional activity of YAP1-TEAD4 complexes that mediate breast cancer cell stemness, metastatic behavior, and evasion of antitumor immunity. This PARP1-mediated mechanism was independent of its role in the DNA damage response. Specifically, PARP1 directly interacted with and promoted the formation of the YAP1-TEAD4 complex by PARylating TEAD4 at a conserved Arg-Lys sequence. This PARP1-enhanced YAP1-TEAD4 binding attenuated the interaction between YAP1 and the E3 ubiquitin ligase CRL4^DCAF12, thus preventing its ubiquitylation and degradation. Furthermore, the abundance of PARP1 protein correlated with that of YAP1 and the immune checkpoint protein PD-L1 in breast cancer tissues and cell lines. In a mouse model of triple-negative breast cancer, pharmacological inhibition of PARP1 enhanced the ability of antibody blockade of PD-L1 to increase cytolytic and tumor-suppressive T cell infiltration and reduce tumor growth. The findings reveal a mechanism that promotes YAP1-TEAD4 transcriptional activity and immune escape in breast cancer cells and is targetable with clinically approved therapies.