Yes-associated protein 1 (YAP) is a transcriptional regulator with critical roles in mechanotransduction, organ size control, and regeneration. Here, we report a robust experimental platform for real-time visualization of native YAP dynamics and target gene expression. Using this platform, we show that activation of YAP target genes is preceded by concerted localization resets, which are dramatic, concerted departure/reentry cycles of nuclear YAP. These resets could be induced by calcium signaling, acto-myosin contractility, and mitotic-exit, and were strictly correlated with YAP-dependent transcription measured using nascent-transcription reporter knockins of YAP target genes. Oncogenically transformed cells with chronically elevated YAP-driven transcription lacked resets but rapidly exchanged YAP between the nucleus and cytoplasm, suggesting an escape from compartmentalization-based control. The single-cell YAP localization and transcription traces suggest a new mode of transcriptional regulation involving the concerted re-partitioning of YAP prior to gene activation.
Results and DiscussionThe YAP (YES-associated protein) / TAZ (transcriptional coactivator with PDZ-binding motif) duo(1), a central node of the Hippo pathway (2)(3), controls organ size, and is critical for mechanotransduction (4)(5)(6). The classic view of YAP signal transduction equates nuclear enrichment with activation of pro-growth transcriptional programs through association with the TEAD family of transcription factors (7) (8) (9). However, other critical signal transducers such as ERK, NfkB and P53 use a rich signal transmission code in which the amplitude, frequency, and duration of their nucleocytoplasmic shuttling all influence gene transcription(10)(11)(12). Given recent reports that both YAP and TEAD can alter subcellular localization(13)(14)(15)(16), we speculated that their subcellular spatiotemporal dynamics may encode upstream signaling information. More generally, we should not expect biological signal transmission circuits to be simple, e.g. a linear mapping between an external input onto downstream gene expression level. There are now many examples of gene circuits with hysteresis, memory, and latching (17)(18)(19)(20)(21). Since these circuits involve spatially-controlled components such as transcription factors, it is natural to wonder about the interplay of cellular spatial dynamics and signal processing.To investigate these ideas, we sought to quantify the localization dynamics of native YAP/TEAD in single cells and relate such dynamics to downstream transcription. We used CRISPR(22) to fluorescently tag native YAP and TEAD in breast epithelial cell lines commonly used for studying hippo signaling(23) (Methods, Figure 1a). Since transcription is pulsatile(24)(25), relating localization dynamics to target gene activity requires real-time measurement of gene transcription. We therefore used CRISPR to tag the native mRNAs of two classic YAP/TEAD targets, ANKRD1 (26) and AREG (27), with 24x-MS2 transcriptional reporters.A recen...