Browsing by Subject "Tumor suppressor gene"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Electrostatic repulsion causes anticooperative DNA binding between tumor suppressor ETS transcription factors and JUN-FOS at composite DNA sites
    (American Society for Biochemistry and Molecular Biology, 2018-11-30) Madison, Bethany J.; Clark, Kathleen A.; Bhachech, Niraja; Hollenhorst, Peter C.; Graves, Barbara J.; Currie, Simon L.; Medicine, School of Medicine
    Many different transcription factors (TFs) regulate gene expression in a combinatorial fashion, often by binding in close proximity to each other on composite cis-regulatory DNA elements. Here, we investigated how ETS TFs bind with the AP1 TFs JUN-FOS at composite DNA-binding sites. DNA-binding ability with JUN-FOS correlated with the phenotype of ETS proteins in prostate cancer. We found that the oncogenic ETS-related gene (ERG) and ETS variant (ETV) 1/4/5 subfamilies co-occupy ETS-AP1 sites with JUN-FOS in vitro, whereas JUN-FOS robustly inhibited DNA binding by the tumor suppressors ETS homologous factor (EHF) and SAM pointed domain-containing ETS TF (SPDEF). EHF bound ETS-AP1 DNA with tighter affinity than ERG in the absence of JUN-FOS, possibly enabling EHF to compete with ERG and JUN-FOS for binding to ETS-AP1 sites. Genome-wide mapping of EHF- and ERG-binding sites in prostate epithelial cells revealed that EHF is preferentially excluded from closely spaced ETS-AP1 DNA sequences. Structural modeling and mutational analyses indicated that adjacent positively charged surfaces from EHF and JUN-FOS use electrostatic repulsion to disfavor simultaneous DNA binding. Conservation of positive residues on the JUN-FOS interface identified E74-like ETS TF 1 (ELF1) as an additional ETS TF exhibiting anticooperative DNA binding with JUN-FOS, and we found that ELF1 is frequently down-regulated in prostate cancer. In summary, divergent electrostatic features of ETS TFs at their JUN-FOS interface enable distinct binding events at ETS-AP1 DNA sites, which may drive specific targeting of ETS TFs to facilitate distinct transcriptional programs.
  • Thumbnail Image
    Item
    EZH2-mediated Downregulation of the Tumor Suppressor DAB2IP Maintains Ovarian Cancer Stem Cells
    (American Association for Cancer Research, 2020-10-15) Zong, Xingyue; Wang, Weini; Ozes, Ali; Fang, Fang; Sandusky, George E.; Nephew, Kenneth P.; Pathology and Laboratory Medicine, School of Medicine
    The majority of women diagnosed with epithelial ovarian cancer (OC) eventually develop recurrence which rapidly evolves into chemoresistant disease. Persistence of ovarian cancer stem cells (OCSC) at the end of therapy may be responsible for emergence of resistant tumors. In this study, we demonstrate that in OCSC, the tumor suppressor Disabled Homolog 2-Interacting Protein (DAB2IP) is silenced by EZH2-mediated H3K27 trimethylation of the DAB2IP promoter. CRISPR/Cas9-mediated deletion of DAB2IP in epithelial OC cell lines upregulated expression of stemness-related genes and induced conversion of non-CSC to CSC, while enforced expression of DAB2IP suppressed CSC properties. Transcriptomic analysis showed that overexpression of DAB2IP in OC significantly altered stemness-associated genes and bioinformatic analysis revealed WNT signaling as a dominant pathway mediating the CSC inhibitory effect of DAB2IP. Specifically, DAB2IP inhibited WNT signaling via downregulation of WNT5B, an important stemness inducer. Reverse Phase Protein Array further demonstrated activation of non-canonical WNT signaling via C-JUN as a downstream target of WNT5B, which was blocked by inhibiting RAC1, a prominent regulator of C-JUN activation. Co-administration of EZH2 inhibitor GSK126 and RAC1 inhibitor NSC23766 suppressed OCSC survival in vitro and inhibited tumor growth and increased platinum sensitivity in vivo. Overall, these data establish that DAB2IP suppresses the cancer stem cell phenotype via inhibition of WNT5B-induced activation of C-JUN and can be epigenetically silenced by EZH2 in OCSC. Targeting the EZH2/DAB2IP/C-JUN axis therefore presents a promising strategy to prevent OC recurrence and has potential for clinical translation.