Clinical Significance of ZNF711 in Human Breast Cancer

Formerly degenerate seventh zinc finger domain from transcription factor ZNF711 rehabilitated by experimental NMR structure

Domain Z7 of nuclear transcription factor ZNF711 has the consensus last metal-ligand H23 found in odd-numbered zinc fingers of this protein replaced by a phenylalanine. Ever since the discovery of ZNF711, it has been thought that Z7 is probably non-functional because of the H23F substitution. The presence of H26 three positions downstream prompted us to examine if this histidine could substitute as the last metal-ligand. The Z7 domain adopts a stable tertiary structure upon metal-binding. The NMR structure of Zn2+-bound Z7 shows the classical ββα-fold of CCHH zinc fingers. Mutagenesis and pH titration experiments indicate that H26 is not involved in metal binding and that Z7 has a tridentate metal-binding site comprised of only residues C3, C6, and H19. By contrast, an F23H mutation that introduces a histidine in the consensus position forms a tetradentate ligand. The structure of the WT Z7 is stable causing restricted ring-flipping of phenylalanines 10 and 23. Dynamics are increased with either the H26A or F23H substitutions and aromatic ring rotation is no longer hindered in the two mutants. The mutations have only small effects on the Kd values for Zn2+ and Co2+ and retain the high thermal stability of the WT domain above 80°C. Like two previously reported designed zinc fingers with the last ligand replaced by water, the WT Z7 domain is catalytically active, hydrolyzing 4-nitrophenyl acetate. We discuss the implications of naturally occurring tridentate zinc fingers for cancer mutations and drug targeting of notoriously undruggable transcription factors.

Formerly degenerate seventh zinc finger domain from transcription factor ZNF711 rehabilitated by experimental NMR structure

Domain Z7 of nuclear transcription factor ZNF711 has the consensus last metal-ligand H23 found in odd-numbered zinc-fingers of this protein replaced by a phenylalanine. Ever since the discovery of ZNF711 it has been thought that Z7 is probably non-functional because of the H23F substitution. The presence of H26 three positions downstream prompted us to examine if this histidine could substitute as the last metal ligand. The Z7 domain adopts a stable tertiary structure upon metal binding. The NMR structure of Zn2+-bound Z7 shows the classical ββα-fold of CCHH zinc fingers. Mutagenesis and pH titration experiments indicate that H26 is not involved in metal binding and that Z7 has a tridentate metal-binding site comprised of only residues C3, C6, and H19. By contrast, an F23H mutation that introduces a histidine in the consensus position forms a tetradentate ligand. The structure of the WT Z7 is stable causing restricted ring-flipping of phenyalanines 10 and 23. Dynamics are increased with either the H26A or F23H substitutions and aromatic ring rotation is no longer hindered in the two mutants. The mutations have only small effects on the Kd values for Zn2+ and Co2+ and retain the high thermal stability of the WT domain above 80 °C. Like two previously reported designed zinc fingers with the last ligand replaced by water, the WT Z7 domain is catalytically active, hydrolyzing 4-nitophenyl acetate. We discuss the implications of naturally occurring tridentate zinc fingers for cancer mutations and drug targeting of notoriously undruggable transcription factors. Our findings that Z7 can fold with only a subset of three metal ligands suggests the recent view that most everything about protein structure can be predicted through homology modeling might be premature for at least the resilient and versatile zinc-finger motif.

The role of zinc finger proteins in malignant tumors

Zinc finger proteins (ZNFs) are the largest family of transcriptional factors in mammalian cells. Recently, their role in the development, progression, and metastasis of malignant tumors via regulating gene transcription and translation processes has become evident. Besides, their possible involvement in drug resistance has also been found, indicating that ZNFs have the potential to become new biological markers and therapeutic targets. In this review, we summarize the oncogenic and suppressive roles of various ZNFs in malignant tumors, including lung, breast, liver, gastric, colorectal, pancreatic, and other cancers, highlighting their role as prognostic markers, and hopefully provide new ideas for the treatment of malignant tumors in the future.

ZNF711 down-regulation promotes CISPLATIN resistance in epithelial ovarian cancer via interacting with JHDM2A and suppressing SLC31A1 expression

Background

Resistance to platinum-based chemotherapy is a major cause of therapeutic failure during the treatment of epithelial ovarian cancer (EOC) patients. Our study aims to elucidate the molecular mechanisms by which ZNF711 down regulation promotes CISPLATIN resistance in EOC.

Methods

ZNF711 expression in 150 EOC specimens was examined using immunohistochemistry. ZNF711 expression and the survival of EOC patients were assessed with a Kaplan-Meier analysis. The effects of ZNF711 expression on CDDP resistance were studied by IC50, Annexin V, and colony formation in vitro, and in an in vivo intra-peritoneal tumor model. The molecular mechanism was determined using a luciferase reporter assay, ChIP assay, CAPTURE approach, and co-IP assay.

Findings

ZNF711 down-regulation exerts a great impact on CDDP resistance for EOC patients by suppressing SLC31A1 and inhibiting CDDP influx. ZNF711 down-regulation promoted, while ZNF711 overexpression drastically inhibited CDDP resistance, both in vivo and in vitro. Mechanistically, the histone demethylase JHDM2A was recruited to the SLC31A1 promoter by ZNF711 and decreased the H3K9me2 level, resulting in the activation of SLC31A1 transcription and enhancement of CDDP uptake. Importantly, co-treatment with the histone methylation inhibitor, BIX-01294, increased the therapeutic efficacy of CDDP treatment in ZNF711-suppressed EOC cells.

Interpretation

These findings both verified the clinical importance of ZNF711 in CDDP resistance and provide novel therapeutic regimens for EOC treatment.

Funding

This work was supported by the Natural Science Foundation of China; Guangzhou Science and Technology Plan Projects; Natural Science Foundation of Guangdong Province; The Fundamental Research Funds for the Central Universities; and China Postdoctoral Science Foundation.

Expression and prognostic analysis of Rho GTPase-activating protein 11A in lung adenocarcinoma

Background

Rho GTPase-activating protein 11A (ARHGAP11A) is a member of the Rho GTPase-activating protein (RhoGAP) subfamily. However, its expression, prognostic significance and clinicopathologic factors correlation in lung adenocarcinoma is still unclear.

Methods

The original gene expression profile, survival data, and clinical information of patients with lung adenocarcinoma (LUAD) were downloaded from The Cancer Genome Atlas (TCGA) database. The expression difference of ARHGAP11A between LUAD tissues and adjacent normal tissues in the TCGA database was analyzed by using R software, and verified by the Oncomine database and immunohistochemical (IHC) assay of LUAD sections. Logistic regression was applied to analyze the relationship between the expression of ARHGAP11A and clinicopathological factors of LUAD. Kaplan-Meier (KM) survival curves and a Cox proportional-hazards model were selected to evaluate the prognostic significance of ARHGAP11A expression. Gene set enrichment analysis (GSEA) software was applied to screen the tumor signaling pathways associated with the low and high expression group of ARHGAP11A in LUAD.

Results

The TCGA database showed that the expression of ARHGAP11A was significantly higher in LUAD tissues than in normal tissues (P<0.001). The up-regulation of ARHGAP11A in LUAD was verified by the Oncomine database (P<0.001) and IHC assay (P<0.001). Logistic regression analysis revealed the high expression of ARHGAP11A to be closely related to age, sex, advanced pathological stage, advanced T stage, and lymph node metastasis. The KM plots based on the TCGA and KM plotter databases indicated that patients with LUAD highly expressing ARHGAP11A had a poorer overall survival (OS) than patients with low expression of ARHGAP11A. Multivariate Cox regression analysis showed that the high expression of ARHGAP11A could be an important independent predictor of a poor prognosis of LUAD [hazards ratio (HR) =1.385; P<0.001]. GSEA indicated that 10 signal pathways were significantly enriched in LUAD samples with the ARHGAP11A expression phenotype.

Conclusions

ARHGAP11A may play a carcinogenic role in the malignant progression of LUAD, and it can be considered as a new independent prognostic factor and potential therapeutic target for LUAD.