Epithelial-to-mesenchymal transition (EMT) is an important process during embryonic development and tumor progression by which adherent epithelial cells acquire mesenchymal properties. Forkhead box protein A1 (FOXA1) is a transcriptional regulator preferentially expressed in epithelial breast cancer cells, and its expression is lost in mesenchymal breast cancer cells. However, the implication of this biased expression of FOXA1 in breast cancer is not fully understood. In this study, we analyzed the involvement of FOXA1 in EMT progression in breast cancer, and found that stable expression of FOXA1 in the mesenchymal breast cancer MDA-MB-231 cells strongly induced the epithelial marker E-cadherin at the mRNA and protein levels. Furthermore, stable expression of FOXA1 was found to reduce the mRNA and protein expression of Slug, a repressor of E-cadherin expression. FOXA1 knockdown in the epithelial breast cancer MCF7 cells reduced E-cadherin protein expression without decreasing its mRNA expression. In addition, FOXA1 knockdown in MCF7 cells up-regulated Slug mRNA and protein expression. Notably, similar to FOXA1 knockdown, stable expression of Slug in MCF7 cells reduced E-cadherin protein expression without decreasing its mRNA expression. Taken together, these results suggest that although FOXA1 can induce E-cadherin mRNA expression, it preferentially promotes E-cadherin expression at the protein level by suppressing Slug expression in epithelial breast cancer, and that the balance of this FOXA1-Slug axis regulates EMT progression.Key words epithelial-mesenchymal transition; E-cadherin; forkhead box protein A1; Slug; estrogen receptor Epithelial-to-mesenchymal transition (EMT) is a process that converts adherent epithelial cells to motile mesenchymal cells during embryonic development. 1) EMT is also involved in tumor progression through inducing metastasis and chemoresistance in tumor cells.2-4) Therefore, a better understanding of the molecular mechanisms underlying EMT in tumor cells is beneficial for development of novel antitumor agents.E-Cadherin is a crucial protein that mediates cell-cell adhesion in epithelial cells.1) E-Cadherin expression is dramatically reduced during EMT, which causes loss of cell-cell adhesion and gain of cell motility. Reduction in E-cadherin expression is mainly caused by the transcriptional repressors of E-cadherin gene (CDH1).2,5) A major transcriptional repressor of CDH1 is the zinc finger factor Slug. Slug binds to the E-box sequences present in the enhancer region of CDH1 and represses its expression. 6)Forkhead box A1 (FOXA1) is a member of the forkhead box family of transcription factors. FOXA1 contains the forkhead DNA-binding domain and the N-and C-terminal transactivation domains.7) FOXA1 regulates expression of many genes involved in the development of various tissues, including mammary gland, liver, midbrain, and lung. 8) FOXA1 is also known to function as a chromatin remodeling factor that opens closed chromatin and facilitates the recruitment of other transcription fa...

The pioneer transcription factor FoxA1 plays an important role in estrogen signaling by opening closed chromatin and promoting recruitment of the estrogen receptor to its target regions in DNA. In this study, we analyzed tyrosine phosphorylation of FoxA1 by the non-receptor-type tyrosine kinase c-Abl. c-Abl was shown to phosphorylate FoxA1 at multiple sites, especially in the N- and C-terminal regions. Tyr429 and Tyr464 were identified as the major phosphorylation sites in the FoxA1 C-terminal region. The phosphomimetic and nonphosphorylatable FoxA1 mutants were generated by glutamic acid and phenylalanine substitutions at these tyrosine residues, respectively. The phosphomimetic FoxA1 promoted the activation of estrogen signaling, whereas the nonphosphorylatable FoxA1 suppressed its activation. Stimulation with the epidermal growth factor, which activates c-Abl, enhanced the activation of estrogen signaling. In contrast, the c-Abl inhibitor imatinib reduced its activation. The phosphomimetic FoxA1 mutant showed a higher affinity toward histone H3 than the wild-type. These results suggest that c-Abl-mediated phosphorylation of FoxA1 promotes the activation of estrogen signaling by inducing its binding to histones. J. Cell. Biochem. 118: 1453-1461, 2017. © 2016 Wiley Periodicals, Inc.

Us3 proteins of herpes simplex virus 1 (HSV-1) and HSV-2 are multi-functional serine-threonine protein kinases. Here, we identified an HSV-2 tegument protein UL7 as a novel physiological substrate of HSV-2 Us3. Mutations in HSV-2 UL7, which precluded Us3 phosphorylation of the viral protein, significantly reduced mortality, viral replication in the vagina, and development of vaginal disease in mice following vaginal infection. These results indicated that Us3 phosphorylation of UL7 in HSV-2 was required for efficient viral replication and pathogenicity in vivo. Of note, this phosphorylation was conserved in UL7 of chimpanzee herpesvirus (ChHV), which phylogenically forms a monophyletic group with HSV-2 and the resurrected last common ancestral UL7 for HSV-2 and ChHV. In contrast, the phosphorylation was not conserved in UL7 of HSV-1, which belongs to a sister clade of the monophyletic group, the resurrected last common ancestral UL7 for HSV-1, HSV-2, and ChHV, and UL7s of other members of the genus Simplexvirus that are phylogenically close to these viruses. Thus, evolution of Us3 phosphorylation of UL7 coincided with the phylogeny of simplexviruses. Furthermore, artificially induced Us3 phosphorylation of UL7 in HSV-1 had no effect on viral replication and pathogenicity in mice in contrast to phosphorylation in HSV-2. Our results suggest that HSV-2 and ChHV have acquired and maintained Us3 phospho-regulation of UL7 during their evolution because the phospho-regulation had an impact on viral fitness in vivo, whereas most other simplexviruses have not because the phosphorylation was not necessary for efficient fitness of the viruses in vivo. IMPORTANCE It has been hypothesized that the evolution of protein phospho-regulation drives phenotypic diversity across species of organisms, which impacts fitness during their evolution. However, there is a lack of information regarding linkage between the evolution of viral phospho-regulation and phylogeny of virus species. In this study, we clarified the novel HSV-2 Us3 phospho-regulation of UL7 in infected cells, which is important for viral replication and pathogenicity in vivo. We also showed that evolution of Us3 phospho-regulation of UL7 was linked to phylogeny of viruses that are phylogenically close to HSV-2 and to phosphorylation requirements for the efficient in vivo viral fitness of HSV-2 and HSV-1, which are representative of viruses that have or have not evolved phospho-regulation, respectively. This study reports the first evidence showing that evolution of viral phospho-regulation coincides with phylogeny of virus species and supports the hypothesis regarding the evolution of viral phospho-regulation during viral evolution.

Transforming growth factor-β (TGF-β) induces apoptosis of normal epithelial cells, such as mammary epithelium. Although breast cancer progression associates with acquisition of resistance to TGF-β-induced apoptosis, the molecular mechanisms underlying this resistance are largely unknown. Here, we show that forkhead box protein A1 (FOXA1), which is known as a pioneer transcription factor, suppresses TGF-β-induced apoptosis of estrogen receptor-positive breast cancer cells. FOXA1 is found to inhibit nuclear translocation of Smad3, a key transcription factor downstream of TGF-β signaling, through suppression of the binding of Smad3 to the nuclear import receptor importin7. Furthermore, RNA sequencing analyses show that knockdown of FOXA1 upregulates Smad3-mediated proapoptotic gene expression. These results demonstrate that FOXA1 as a potent survival factor that suppresses TGF-β-induced apoptosis by inhibiting Smad3 signaling in estrogen receptor-positive breast cancer cells. Thus, we provide evidence for the first time that FOXA1 localizing to the cytoplasm negatively regulates Smad3-induced apoptosis in TGF-β-mediated signal transduction.

The identification of cellular protein(s) that interact with viral effector proteins and function in important viral procedures is necessary for enhancing our understanding of the mechanics of various viral processes. In this study, we established a new system consisting of interactome screening for the herpes simplex virus 1 (HSV-1) nuclear egress complex (NEC), followed by loss-of-function screening to target the identified putative NEC-interacting cellular proteins to detect a defect in HSV-1 nuclear egress.