YAP and TAZ are transcriptional co-activators of AP-1 proteins and STAT3 during breast cellular transformation

Abstract

The YAP and TAZ paralogues are transcriptional co-activators recruited to target sites, primarily by TEAD proteins. Here, we show that YAP and TAZ are also recruited by JUNB and STAT3, key factors that mediate an epigenetic switch linking inflammation to cellular transformation. YAP and TAZ directly interact with JUNB and STAT3 via a WW domain important for transformation, co-occupy many target sites in vivo via AP-1 and (to a lesser extent) STAT3 sequence motifs, and stimulate transcriptional activation by AP-1 proteins. A few target sites are YAP- or TAZ-specific, and they are associated with different sequence motifs and gene classes. YAP/TAZ, JUNB, and STAT3 directly regulate a common set of target genes that overlap, but are distinct from, those regulated by YAP/TAZ and TEADs. The set of genes regulated by YAP/TAZ, STAT3, and JUNB is associated with poor survival in breast cancer patients with the triple-negative form of the disease.

MafB, WDR77, and ß-catenin interact with each other and have similar genome association profiles

“…Third, biological replicates that involved different chromatin samples gave reproducible results. Fourth, using the same procedure and sometimes the same chromatin samples, the unexpected pattern was not observed in ChIP-seq experiments for YAP, TAZ, or TEAD (He et al, 2021) or other proteins (e.g. the example locus in Figure 4A).…”

“…Co-IP experiments were performed on separated nuclear and cytoplasmic compartments as described previously (He et al, 2021) using antibodies against β-catenin antibody (BD Bioscience, Cat # 610154), WDR77 (Cell Signaling, Cat# 2018), and MafB (Cell Signaling, Cat# 41019). Western blots were performed as described previously (Ji et al, 2019; He et al 2021) using antibodies against β-catenin (Cell Signaling, Cat#9581), WDR77 (SCBT, Cat# sc-100899), MafB (SCBT, Cat# sc-10022), MEK1/2 (Bethyl Laboratories, Cat# A302-140A-T), U1 SnRNP70 (SCBT, Cat# sc-9571), and H3 (Abcam, Cat# AB1791). For assessing direct interactions, recombinant β-catenin, WDR77, and MafB proteins (expressed from pET plasmids in BL21 E. coli cells) were produced as described previously (He et al 2021) and analyzed by co-IP.…”

“…Western blots were performed as described previously (Ji et al, 2019; He et al 2021) using antibodies against β-catenin (Cell Signaling, Cat#9581), WDR77 (SCBT, Cat# sc-100899), MafB (SCBT, Cat# sc-10022), MEK1/2 (Bethyl Laboratories, Cat# A302-140A-T), U1 SnRNP70 (SCBT, Cat# sc-9571), and H3 (Abcam, Cat# AB1791). For assessing direct interactions, recombinant β-catenin, WDR77, and MafB proteins (expressed from pET plasmids in BL21 E. coli cells) were produced as described previously (He et al 2021) and analyzed by co-IP.…”

“…In addition, cellular transformation depends on transcriptional co-activators that are key components of signal transduction pathways and are recruited to target sites by DNA-binding proteins. Such co-activators include the YAP and TAZ paralogues, the ultimate targets of the Hippo signaling pathway, (He et al, 2021), and the calcium-binding cytokines S100A8 and S100A9 (Song and Struhl, 2021).…”

Mechanisms of YAP/TAZ transcriptional control

“…The widespread presence of AP-1 sites at YAP/TAZ regulated genes raises questions on to what extent targeting the YAP/TAZ-TEAD interaction may be in fact sufficient to blunt YAP/TAZ-driven tumorigenesis. YAP has been indeed shown to bind directly to AP-1, and recent work by K. Struhl and colleagues proposes that YAP/TAZ may serve as transcriptional co-activators of JUNB to control a set of genes active during cell transformation, but that only in part overlap with those regulated by YAP/TAZ/TEAD [25]. Clearly, more work is required to dissect the cooperative vs. potentially redundant roles of TEAD and AP-1, and to gauge the contribution of AP-1 factors to YAP/TAZ biology in cancer.…”