Unbiased discovery of interactions at a control locus driving expression of the cancer-specific therapeutic and diagnostic target, mesothelin

Discovery of Covalent Inhibitors Targeting the Transcriptional Enhanced Associate Domain Central Pocket

Transcriptional enhanced associate domain (TEAD) transcription factors together with coactivators and corepressors modulate the expression of genes that regulate fundamental processes, such as organogenesis and cell growth, and elevated TEAD activity is associated with tumorigenesis. Hence, novel modulators of TEAD and methods for their identification are in high demand. We describe the development of a new “thiol conjugation assay” for identification of novel small molecules that bind to the TEAD central pocket. The assay monitors prevention of covalent binding of a fluorescence turn-on probe to a cysteine in the central pocket by small molecules. Screening of a collection of compounds revealed kojic acid analogues as TEAD inhibitors, which covalently target the cysteine in the central pocket, block the interaction with coactivator yes-associated protein with nanomolar apparent IC₅₀ values, and reduce TEAD target gene expression. This methodology promises to enable new medicinal chemistry programs aimed at the modulation of TEAD activity.

Targeting the Hippo Pathway and Cancer through the TEAD Family of Transcription Factors

The Hippo pathway is a critical transcriptional signaling pathway that regulates cell growth, proliferation and organ development. The transcriptional enhanced associate domain (TEAD) protein family consists of four paralogous transcription factors that function to modulate gene expression in response to the Hippo signaling pathway. Transcriptional activation of these proteins occurs upon binding to the co-activator YAP/TAZ whose entry into the nucleus is regulated by Lats1/2 kinase. In recent years, it has become apparent that the dysregulation and/or overexpression of Hippo pathway effectors is implicated in a wide range of cancers, including prostate, gastric and liver cancer. A large body of work has been dedicated to understanding the therapeutic potential of modulating the phosphorylation and localization of YAP/TAZ. However, YAP/TAZ are considered to be natively unfolded and may be intractable as drug targets. Therefore, TEAD proteins present themselves as an excellent therapeutic target for intervention of the Hippo pathway. This review summarizes the functional role of TEAD proteins in cancer and assesses the therapeutic potential of antagonizing TEAD function in vivo.

Zinc finger protein 191 inhibits hepatocellular carcinoma metastasis through discs large 1-mediated yes-associated protein inactivation

Interplay between cell polarity module Scribble-Lethal Giant Larvae-Discs Large 1 (DLG1) and Yes-associated protein (YAP) appears critical in tumor metastasis. We identified zinc finger protein 191 (ZNF191) as a metastasis suppressor acting through DLG-YAP crosstalk in hepatocellular carcinoma (HCC). Overexpression of ZNF191 in HCC cells impaired cell motility, while ZNF191 depletion promoted cell migration in vitro and metastasis in vivo through triggering YAP signaling. Chromatin immunoprecipitation-sequencing revealed that ZNF191 specifically bound to the promoter of DLG1, a cell polarity maintainer and a negative regulator of YAP. The binding sequence of ZNF191 at the DLG1 promoter is a seven-repeat of TCAT motif. Double-knockdown experiments inferred that DLG1 was not only the mediator of the function of ZNF191 to suppress migration but also a link between ZNF191 and YAP signaling. Decreased expression of ZNF191 in human metastatic HCC specimens correlated positively with DLG1 levels but inversely with YAP activation. Our findings illustrate a YAP-targeting, antimetastasis function of ZNF191, thereby representing a possible prognostic marker and a potential target for metastasis therapy.

CONCLUSION

ZNF191 directly binds to the DLG1 promoter at a typical TCAT repeating motif and activates the expression of DLG1; through up-regulating DLG1, ZNF191 inhibits cell migration and YAP activation in HCC cells and eventually inhibits metastasis. (Hepatology 2016;64:1148-1162).

Broader implications of SILAC-based proteomics for dissecting signaling dynamics in cancer

Large-scale transcriptome and epigenome analyses have been widely utilized to discover gene alterations implicated in cancer development at the genetic level. However, mapping of signaling dynamics at the protein level is likely to be more insightful and needed to complement massive genomic data. Stable isotope labeling with amino acids in cell culture (SILAC)-based proteomic analysis represents one of the most promising comparative quantitative methods that has been extensively employed in proteomic research. This technology allows for global, robust and confident identification and quantification of signal perturbations important for the progress of human diseases, particularly malignancies. The present review summarizes the latest applications of in vitro and in vivo SILAC-based proteomics in identifying global proteome/phosphoproteome and genome-wide protein-protein interactions that contribute to oncogenesis, highlighting the recent advances in dissecting signaling dynamics in cancer.

Mass spectrometry-based identification of proteins interacting with nucleic acids

The identification of the regulatory proteins that control DNA transcription as well as RNA stability and translation represents a key step in the comprehension of gene expression regulation. Those proteins can be purified by DNA- or RNA-affinity chromatography, followed by identification by mass spectrometry. Although very simple in the concept, this represents a real technological challenge due to the low abundance of regulatory proteins compared to the highly abundant proteins binding to nucleic acids in a nonsequence-specific manner. Here we review the different strategies that have been set up to reach this purpose, discussing the key parameters that should be considered to increase the chances of success. Typically, two categories of biological questions can be distinguished: the identification of proteins that specifically interact with a precisely defined binding site, mostly addressed by quantitative mass spectrometry, and the identification in a non-comparative manner of the protein complexes recruited by a poorly characterized long regulatory region of nucleic acids. Finally, beside the numerous studies devoted to in vitro-assembled nucleic acid-protein complexes, the scarce data reported on proteomic analyses of in vivo-assembled complexes are described, with a special emphasis on the associated challenges.