Abstract PR02: Spatial resets modulate YAP-dependent transcription

Abstract

Abstract Despite the emergence of YAP as an important regulator of cell proliferation and oncogenesis, a clear picture of the relationship between YAP localization dynamics and downstream transcription is missing. Using live-cell imaging of CRISPR-knockin breast epithelial lines, we show that YAP displays dramatic spatial resets characterized by bulk exit from the nucleus followed by re-entry. These localization resets were upregulated by inhibiting Src-kinase and dampened by Ras transformation. After monolayer wounding, we found that edge-cells exhibited a synchronized localization reset. Lastly, induction of store-operated Ca2+ release and chromatin condensation during mitosis were found to also cause YAP localization resets. We relate these spatiotemporal YAP localization changes to transcriptional outputs from endogenous YAP targets using nascent-transcription reporter-cassette knockins. Maximal transcriptional responses were strictly correlated to the induction of localization resets through targeting Src-kinase, inducing Ca2+ release, and mitosis. By blocking the response to Ca2+ release using a PKC inhibitor, we show that the large transcriptional response is dependent on the ability of YAP to transiently localize to the cytoplasm. We found that Ras transformation, which suppressed YAP localization resets, caused upregulated import and export, reduced overall chromatin binding, and increased target gene expression. Untransformed cells, on the other hand, show relatively high nuclear retention through increased binding and slower nuclear export. This suggests that Ras transformation allows an escape from the compartmentalization-based control shown in untransformed cells. Our results suggest a new perspective on YAP-dependent transcription, revealed through the application of real-time imaging of native YAP dynamics and nascent transcription of YAP target genes. This abstract is also being presented as Poster A21. Citation Format: Matt Franklin, Raja Ghosh, Quanming Shi, Jan Liphardt. Spatial resets modulate YAP-dependent transcription [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr PR02.