Search for: All records

The Polycomb group protein SCML2 and the transcriptional cofactor YAP1 regulate diverse cellular biology, including stem cell maintenance, developmental processes, and gene regulation in mammals and flies. However, their molecular and functional interactions are unknown. Here, we show that SCML2 interacts with YAP1, as revealed by immunological assays and mass spectroscopy. We have demonstrated that the steroid hormone androgen regulates the interaction of SCML2 with YAP1 in human tumor cell models. Our proximity ligation assay and GST pulldown showed that SCML2 and YAP1 physically interacted with each other. Silencing SCML2 by RNAi changed the growth behaviors of cells in response to androgen signaling. Mechanistically, this phenomenon is attributed to the interplay between distinct chromatin modifications and transcriptional programs, likely coordinated by the opposing SCML2 and YAP1 activity. These findings suggest that YAP1 and SCML2 cooperate to regulate cell growth, cell survival, and tumor biology downstream of steroid hormones. 

Abstract The EPHA3 protein tyrosine kinase, a member of the ephrin receptor family, regulates cell fate, cell motility, and cell–cell interaction. These cellular events are critical for tissue development, immunological responses, and the processes of tumorigenesis. Earlier studies revealed that signaling via the STK4 -encoded MST1 serine-threonine protein kinase, a core component of the Hippo pathway, attenuated EPHA3 expression. Here, we investigated the mechanism by which MST1 regulates EPHA3. Our findings have revealed that the transcriptional regulators YAP1 and TEAD1 are crucial activators of EPHA3 transcription. Silencing YAP1 and TEAD1 suppressed the EPHA3 protein and mRNA levels. In addition, we identified putative TEAD enhancers in the distal EPHA3 promoter, where YAP1 and TEAD1 bind and promote EPHA3 expression. Furthermore, EPHA3 knockout by CRISPR/Cas9 technology reduced cell–cell interaction and cell motility. These findings demonstrate that EPHA3 is transcriptionally regulated by YAP1/TEAD1 of the Hippo pathway, suggesting that it is sensitive to cell contact-dependent interactions. 

The transcriptional coactivator YAP1 (yes-associated protein 1) regulates cell proliferation, cell–cell interactions, organ size, and tumorigenesis. Post-transcriptional modifications and nuclear translocation of YAP1 are crucial for its nuclear activity. The objective of this study was to elucidate the mechanism by which the steroid hormone androgen regulates YAP1 nuclear entry and functions in several human prostate cancer cell lines. We demonstrate that androgen exposure suppresses the inactivating post-translational modification phospho–Ser-127 in YAP1, coinciding with increased YAP1 nuclear accumulation and activity. Pharmacological and genetic experiments revealed that intact androgen receptor signaling is necessary for androgen's inactivating effect on phospho–Ser-127 levels and increased YAP1 nuclear entry. We also found that androgen exposure antagonizes Ser/Thr kinase 4 (STK4/MST1) signaling, stimulates the activity of protein phosphatase 2A, and thereby attenuates the phospho–Ser-127 modification and promotes YAP1 nuclear localization. Results from quantitative RT-PCR and CRISPR/Cas9–aided gene knockout experiments indicated that androgen differentially regulates YAP1-dependent gene expression. Furthermore, an unbiased computational analysis of the prostate cancer data from The Cancer Genome Atlas revealed that YAP1 and androgen receptor transcript levels correlate with each other in prostate cancer tissues. These findings indicate that androgen regulates YAP1 nuclear localization and its transcriptional activity through the androgen receptor–STK4/MST1–protein phosphatase 2A axis, which may have important implications for human diseases such as prostate cancer. 

Dysregulation of the receptor tyrosine kinases (RTKs) by means of mutation, amplification or overexpression plays a crucial role in cell growth, cell survival, cell motility during cancer progression and metastasis. EPHA3 (erythropoietin-producing hepatocellular carcinoma cell surface type A receptor 3) is a member of the RTKs. Evidence indicates that the upregulation of the EPHA3 activity is implicated in the pathobiology of various cancers, including prostate cancer, and thus, it is a prime therapeutic target in cancer. However, the role of EPHA3 signaling in prostate cancer progression remains obscure. Currently, the development of castration-resistant prostate cancer (CRPC) poses a clinical challenge because it is lethal. The molecular mechanisms that contribute to lethal prostate cancer are largely unknown. The objective of this study is to investigate whether EPHA3 signaling plays a critical role in prostate cancer progression and therapeutic relapse. Our analysis of the prostate cancer public datasets revealed that the EPHA3 gene was amplified up to 19% of metastatic CRPC cases with the neuroendocrine phenotype. Our immunological assay confirmed the positive staining of EPHA3 protein in human prostate cancer specimens. Our semi-quantitative and quantitative PCR assays demonstrated that the levels of EPHA3 vary among established prostate cancer cell lines. Nevertheless, we consistently found that the levels of EPHA3 mRNA in CRPC cell line, C4-2, were 3-fold higher than its castration-sensitive parental LNCaP cells. Furthermore, we demonstrated that an increase in expression of EPHA3 mRNA in C4-2 compared with LNCaP cells coincided with the upregulation of the EPHA3 protein, as independently confirmed by western blotting and immunofluorescence imaging. These findings indicate that EPHA3 may confer an aggressive prostate cancer cell phenotype. Because androgen receptor (AR) signaling is a potent mediator of CRPC cell growth and survival, the targeting of EPHA3 signaling alone or together with AR may improve the efficacy of current therapies for patients with advanced prostate cancer.