The common and mutual exclusive interactome of the oncogenes YAP and TAZ in liver cancer

The Hippo pathways effectors yes-associated protein (YAP) and WW domain containing transcription regulator 1 (WWTR1; syn: TAZ) play an important role in tumor development and progression. Recent findings illustrate that both oncogenes facilitate their pro-tumorigenic properties in liver cancer via common and exclusive mechanisms. However, the underlying molecular network of YAP- and TAZ-induced tumorigenesis is not fully understood. Here, we aim to dissect their respective interactome in liver cancer cells.

We generated HCC cell lines expressing inducible YAP or TAZ tagged with the biotin ligase BirA, which allows labelling of potential binding partners. After biotin administration for 18 hours, biotin-tagged proteins from 4 technical replicates were pulled-down by streptavidin. Purified proteins were seperated by SDS-PAGE and submitted to tryptic in-gel digestion. The LC/MS analysis was performed using an Easy-nLC 1200 coupled to an Orbitrap Exploris 480 MS. The resulting data was analyzed using MaxQuant and Perseus software. Only proteins with a fold change >2 and a false discovery rate <0.05 compared to the control were considered for further analyses. CoIP was performed for candidate validation.

According to the selection criteria, 267 potential YAP and/or TAZ binding partners were identified among them many already known interaction factors such as transcriptions factors (TEAD family), Hippo pathway constituents (e.g. LATS) and cell junction proteins (e.g. AMOT). With 247 proteins the identified YAP interactome was bigger than the TAZ interactome with 108 potential binding partners. Interestingly, most predicted TAZ binding partner (81 %; 88/108) also interact with YAP. In contrast, for YAP the majority of binding partners was not recognized by TAZ (64 %, 159/247). STRING database analysis revealed involvement of the YAP/TAZ interactome in several cancer cell-relevant processes like chromatin remodeling, proliferation, cell polarity and actin dynamics. Remarkably the YAP exclusive interactome contains a vast amount of proteins involved in cytoskeletal remodeling and cell junctions. CoIP experiments confirmed binding of YAP with so far unkown interaction partners such as vasodilator stimulated phosphoprotein (VASP), which supports actin polymerization.

On the molecular level the majority of the TAZ interactome is also recognized by YAP in HCC cells. Thus, YAP may facilitate additional functions via interactions with YAP-exclusive binding partners.

Publication History

Article published online:
04 January 2021