Kaiso Is a Novel TAZ-Interaction Partner That Promotes Hepatic Stellate Cell Activation and Regulates the Downstream...

Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are key regulators of hepatic stellate cell (HSC) activation and liver fibrosis. While the canonical YAP/TAZ-TEAD axis is well-characterized, non-canonical interaction partners and downstream long non-coding RNAs (lncRNAs) that orchestrate fibrogenic programs in HSCs remain undefined. Using BioID and next-generation sequencing (NGS) in LX-2 cells, we identified YAP/TAZ-interactomes and YAP/TAZ-regulated lncRNAs. BioID results and proximity ligation assay (PLA) identified the transcription factor Kaiso as a TAZ interaction partner. Functionally, Kaiso knockdown suppressed key aspects of HSC activation in LX-2 cells. We next integrated our NGS results from YAP/TAZ-knockdown in LX-2 cells with publicly available Kaiso ChIP-seq data. This identified HIF1A-AS3 as a common downstream lncRNA. ChIP-qPCR confirmed direct binding of Kaiso to the HIF1A-AS3 promoter. Furthermore, HIF1A-AS3 silencing mirrored the functional effects of Kaiso knockdown. Global proteomic profiling following knockdown of TAZ, Kaiso, or HIF1A-AS3 revealed a network of commonly regulated proteins enriched for pathways central to HSC activation. In conclusion, we establish Kaiso as a novel TAZ interaction partner and identify HIF1A-AS3 as a shared downstream target of TAZ and Kaiso, suggesting a potential profibrotic regulatory network that promotes HSC activation and may represent a therapeutic target for liver fibrosis.