De-differentiation by Adenovirus E1A Due to Inactivation of Hippo Pathway Effectors YAP and TAZ [ChIP-seq]

Adenovirus-transformed cells have a de-differentiated phenotype. Eliminating E1A in transformed human embryonic kidney cells de-repressed ~2600 genes, generating a gene expression profile closely resembling mesenchymal stem cells (MSC). This was associated with a dramatic change in cell morphology from one with scant cytoplasm and a globular nucleus to one with increased cytoplasm, extensive actin stress fibers and actomyosin-dependent flattening against the substratum. E1A-induced histone hypoacetylation by p300/CBP at H3K27/18 was reversed. Most of the increase in H3K27/18ac was near TEAD transcription factors associated with their co-activators YAP and TAZ regulated by the Hippo pathway. E1A causes YAP/TAZ cytoplasmic sequestration. After eliminating E1A, YAP/TAZ were transported into nuclei where they associated with poised enhancers with DNA-bound TEAD4 and H3K4me1. This activation of YAP/TAZ required RHO-family GTPase signaling and caused histone acetylation by p300/CBP, chromatin remodeling, and cohesin loading to establish MSC-associated enhancers and then super-enhancers. Consistent results were also observed in rat embryo kidney cells, human fibroblasts and human respiratory tract epithelial cells. These results together with earlier studies suggest that YAP/TAZ function in a developmental check-point controlled by signaling from the actin cytoskeleton that prevents differentiation of a progenitor cell until it is in the correct cellular and tissue environment. Examination of YAP, H3K18ac, H3K27ac, H3K4me1, TEAD1, TEAD4, RAD21, chromatin accessibility and mRNA by ChIP-seq, ATAC-seq, and mRNA-seq