Transcription of human zinc finger ZNF268 gene requires an intragenic promoter element

TBK1-stabilized ZNF268a recruits SETD4 to methylate TBK1 for efficient interferon signaling

Sufficient activation of interferon signaling is critical for the host to fight against invading viruses, in which post-translational modifications have been demonstrated to play a pivotal role. Here, we demonstrate that the human KRAB-zinc finger protein ZNF268a is essential for virus-induced interferon signaling. We find that cytoplasmic ZNF268a is constantly degraded by lysosome and thus remains low expressed in resting cell cytoplasm. Upon viral infection, TBK1 interacts with cytosolic ZNF268a to catalyze the phosphorylation of Serine 178 of ZNF268a, which prevents the degradation of ZNF268a, resulting in the stabilization and accumulation of ZNF268a in the cytoplasm. Furthermore, we provide evidence that stabilized ZNF268a recruits the lysine methyltransferase SETD4 to TBK1 to induce the mono-methylation of TBK1 on lysine 607, which is critical for the assembly of the TBK1 signaling complex. Notably, ZNF268 S178 is conserved among higher primates but absent in rodents. Meanwhile, rodent TBK1 607th aa happens to be replaced by arginine, possibly indicating a species-specific role of ZNF268a in regulating TBK1 during evolution. These findings reveal novel functions of ZNF268a and SETD4 in regulating antiviral interferon signaling.

The Expression of ZNF268 and Its Role in The Cisplatin-based Chemoresistance of Breast Cancer

Objective

Breast cancer is one of the most prevalent cancers in females worldwide and is one of the leading causes of cancer death and disability in women. Multiple therapies have been applied to breast cancer treatment; however, the long-term survival rate remains low. Although cisplatin has been widely utilized for cancer therapy, chemoresistance still influences the outcome.

Methods

After collecting the breast cancer cell line MDA-MB-231 treated with or without cisplatin and sample information from The Cancer Genome Atlas Program (TCGA), we screened out their common parameters and influences on the prognoses of patients' potential targets. Surgical excisional tissue sections of patients with breast cancer who were admitted and treated in the Department of Breast and Thyroid Surgery, Liuzhou People's Hospital from 2017 to 2020 was collected and follow up. After a series of assays combined with clinical information, we tested the reliability of the target.

Results

We found that a high expression level of ZNF268 in breast cancer cell lines significantly enhances the sensitivity to cisplatin, contrary to the effects of low expression. Furthermore, a significantly worse prognosis was observed in patients with a high expression of ZNF268 after cisplatin chemotherapy.

Conclusion

The expression level of ZNF268 in breast cancer patients after cisplatin chemotherapy may become a potential target to predict the chemoresistance of patients to cisplatin. This study provides a novel idea for improving breast cancer treatment and survival rates.

KRAB-Zinc Finger Protein ZNF268a Deficiency Attenuates the Virus-Induced Pro-Inflammatory Response by Preventing IKK Complex Assembly

Despite progress in understanding how virus-induced, NF-κB-dependent pro-inflammatory cytokines are regulated, there are still factors and mechanisms that remain to be explored. We aimed to uncover the relationship between KRAB-zinc finger protein ZNF268a and NF-κB-mediated cytokine production in response to viral infection. To this end, we established a ZNF268a-knockout cell line using a pair of sgRNAs that simultaneously target exon 3 in the coding sequence of the ZNF268 gene in HEK293T. HEK293T cells lacking ZNF268a showed less cytokine expression at the transcription and protein levels in response to Sendai virus/vesicular stomatitis virus (SeV/VSV) infection than wild-type cells. Consistent with HEK293T, knock-down of ZNF268a by siRNAs in THP-1 cells significantly dampened the inflammatory response. Mechanistically, ZNF268a facilitated NF-κB activation by targeting IKKα, helping to maintain the IKK signaling complex and thus enabling proper p65 phosphorylation and nuclear translocation. Taken together, our data suggest that ZNF268a plays a positive role in the regulation of virus-induced pro-inflammatory cytokine production. By interacting with IKKα, ZNF268a promotes NF-κB signal transduction upon viral infection by helping to maintain the association between IKK complex subunits.

Zinc fingers function cooperatively with KRAB domain for nuclear localization of KRAB-containing zinc finger proteins

Multiple nuclear localization domains have been identified in nuclear proteins, and they finely control nuclear import and functions of those proteins. ZNF268 is a typical KRAB-containing zinc finger protein (KRAB-ZFP), and previous studies have shown that the KRAB domain reinforces nuclear localization of KRAB-ZFPs by interacting with KAP1. In this study, we find that some of 24 zinc fingers of ZNF268 also possess nuclear localization activity. Results of mutagenesis studies suggest that KRAB and zinc fingers are both necessary, and they function both independently and cooperatively for the nuclear localization of ZNF268. However, the subnuclear targeting activities of KRAB and zinc fingers are different. KRAB targets proteins in nucleoplasm, but not in the nucleolus, which is mediated by interaction with KAP1, while zinc fingers target proteins in the whole nucleus uniformly. The cooperative activities of KAP1-KRAB-zinc fingers result in the precise nucleoplasmic, but not nucleolar localization of KRAB-ZFPs. Our studies reveal a novel mechanism for the subcellular localization of KRAB-ZFPs and may help us to further explore their biological functions.

Aberrant expression of ZNF268 alters the growth and migration of ovarian cancer cells

Ovarian cancer is one of the most lethal gynaecological cancers worldwide. However, the mechanisms underlying ovarian carcinogenesis are not well understood. The present study used immunostaining, western blotting and quantitative real-time PCR to demonstrate that ZNF268 is overexpressed in human ovarian carcinomas. ZNF268-knockdown increased the viability, colony formation and growth of in vivo xenografts of ovarian carcinoma SKOV-3 cells, whereas SKOV-3 cell migration was inhibited. Furthermore, it was demonstrated that the knockdown of ZNF268 may increase SKOV-3 cell growth by promoting cell cycle progression. The findings suggest that ZNF268 is a novel protein involved in ovarian carcinogenesis and that it may aid in the understanding of the mechanisms of ovarian carcinogenesis.

The zinc finger protein ZNF268 is overexpressed in human cervical cancer and contributes to tumorigenesis via enhancing NF-κB signaling

Cervical cancer is one of the most common tumors affecting women's health worldwide. Although human papillomavirus can be detected in nearly all cases, the mechanism of cervical carcinogenesis remains to be further addressed. Here, we demonstrated that ZNF268, a Krüppel-associated box-containing zinc finger protein, might contribute to the development of cervical cancer. We found that ZNF268b2, an isoform of ZNF268, was overexpressed in human squamous cervical cancer specimens. Knockdown of ZNF268 in cervical cancer cells caused cell cycle arrest at the G(0)/G(1) phase, reduced colony formation, and increased sensitivity to TNFα-induced apoptosis. In addition, HeLa cell growth in xenograft nude mice was suppressed by ZNF268 knockdown, with increased apoptosis. Furthermore, ZNF268b2 was shown to increase NF-κB signaling in vitro and in vivo. Reconstitution of NF-κB activity restored proliferation in ZNF268 knockdown HeLa cells. Of note, we observed a high frequency of NF-κB activation in ZNF268-overexpressing cervical cancer tissues, suggesting a pathological coincidence of ZNF268b2 overexpression and NF-κB activation. Taken together, our results reveal a novel role of ZNF268b2 that contributes to cervical carcinogenesis in part through enhancing NF-κB signaling.

Overexpression of the human ZNF300 gene enhances growth and metastasis of cancer cells through activating NF-kB pathway

Zinc finger proteins (ZNF) play important roles in various physiological processes. Here we report that ZNF300, a novel zinc finger protein, identified specifically in humans, promotes tumour development by modulating the NF-κB pathway. Inflammatory factors were found to induce ZNF300 expression in HeLa cell line, and ZNF300 expression further enhanced NF-κB signalling by activating TRAF2 and physically interacting with IKKβ. Furthermore, ZNF300 overexpression increased ERK1/2 phosphorylation and the expression of c-myc, IL-6, and IL-8 but decreased the expression of p21^waf-1 and p27^Kip1; whose down-regulation led to the opposite effect. Most importantly, ZNF300 overexpression stimulated cancer cell proliferation in vitro and significantly enhanced tumour development and metastasis in mouse xenograft model, while knocking down ZNF300 led to the opposite effects. We have identified a novel function for ZNF300 in tumour development that may uniquely link inflammation and NF-κB to tumourigenesis in humans but not in mice.

Knockdown of ZNF268, which is transcriptionally downregulated by GATA-1, promotes proliferation of K562 cells

The human ZNF268 gene encodes a typical KRAB-C2H2 zinc finger protein that may participate in hematopoiesis and leukemogenesis. A recent microarray study revealed that ZNF268 expression continuously decreases during erythropoiesis. However, the molecular mechanisms underlying regulation of ZNF268 during hematopoiesis are not well understood. Here we found that GATA-1, a master regulator of erythropoiesis, repressed the promoter activity and transcription of ZNF268. Electrophoretic mobility shift assays and chromatin immunoprecipitation assays showed that GATA-1 directly bound to a GATA binding site in the ZNF268 promoter in vitro and in vivo. Knockdown of ZNF268 in K562 erythroleukemia cells with specific siRNA accelerated cellular proliferation, suppressed apoptosis, and reduced expression of erythroid-specific developmental markers. It also promoted growth of subcutaneous K562-derived tumors in nude mice. These results suggest that ZNF268 is a crucial downstream target and effector of GATA-1. They also suggest the downregulation of ZNF268 by GATA-1 is important in promoting the growth and suppressing the differentiation of K562 erythroleukemia cells.

A novel zinc finger protein Zfp637 behaves as a repressive regulator in myogenic cellular differentiation

Zinc finger proteins have been implicated as transcription factors in the differentiation and development of cells and tissues in higher organisms. The classical C2H2 zinc finger motif is one main type of motif of zinc finger proteins. Our previous studies have shown that Zfp637, which comprises six consecutively typical and one atypical C2H2 zinc finger motifs, is highly expressed in undifferentiated or poorly differentiated cell lines, but is moderately or slightly expressed in normal tissues. We have also demonstrated that Zfp637 can promote cell proliferation. However, its role in the regulation of cell differentiation remains unknown. We report here that endogenous Zfp637 as well as mTERT is expressed in proliferating C2C12 myoblasts and that their expression is downregulated during myogenic differentiation. Constitutive expression of Zfp637 in C2C12 myoblasts increased mTERT expression and telomerase activity, and promoted the progression of the cell cycle and cell proliferation. By contrast, endogenous repression of Zfp637 expression by RNA interference downregulated the mTERT gene and the activity of telomerase, and markedly reduced cell proliferation. Overexpression of Zfp637 also inhibited the expression of myogenic differentiation-specific genes such as MyoD and myogenin, and prevented C2C12 myoblast differentiation. Our results suggest that Zfp637 inhibits muscle differentiation through a defect in the cell cycle exit by potentially regulating mTERT expression in C2C12 myoblasts. This may provide a new research line for studying muscle differentiation.

PU.1 can regulate the ZNF300 promoter in APL-derived promyelocytes HL-60

ZNF300, which plays the role in human embryonic development and some diseases, is a typical KRAB/C2H2 zinc finger gene expressed only in higher mammalians. Our data showed that expression of ZNF300 changed significantly in various leukemia blasts in the bone marrow aspirates of newly diagnosed leukemia patients. To investigate the potential relationship between expression of ZNF300 and the progression of leukemia development and hematopoietic differentiation, we cloned and characterized the putative human ZNF300 gene promoter and identified its transcription start sites (TSSs). Deletion and mutagenesis analysis demonstrated that a myeloid-specific transcription factor PU.1 binding site was responsible for myeloid-specific regulation of ZNF300 promoter activity. Furthermore, electrophoretic mobility shift and chromatin immunoprecipitation assays revealed that PU.1 bound to the PU.1 binding site within ZNF300 promoter region in vitro and in vivo. Overexpression of PU.1 elevated ZNF300 promoter activity, whereas silencing of PU.1 expression significantly reduced the activity in myeloid-derived HL-60 cell but not in T-cell Jurkat. In vitro induced HL-60 cells into CD11b expressing cells by DMSO demonstrated that ZNF300 was upregulated along with upregulation of PU.1 expression. These results demonstrated that ZNF300 was activated by PU.1 and suggested that the regulation may be involved in the progression of leukemia development and hematopoietic differentiation.

Gene expression atlas for human embryogenesis

Human embryogenesis is believed to involve an integrated set of complex yet coordinated development of different organs and tissues mediated by the changes in the spatiotemporal expression of many genes. Here, we report a genome-wide expression analysis during wk 4-9 of human embryogenesis, a critical period when most organs develop. About half of all human genes are expressed, and 18.6% of the expressed genes were significantly regulated during this important period. We further identified >5000 regulated genes, most of which previously were not known to be associated with animal development. Our study fills an important gap in mammalian developmental studies by identifying functional pathways involved in this critical but previously not studied period. Our study also revealed that the genes involved here are distinct from those during early embryogenesis, which include three groups of maternal genes. Furthermore, we discovered that genes in a given developmental process are regulated coordinately. This led us to develop an easily searchable database of this entire collection of gene expression profiles, allowing for the identification new genes important for a particular developmental process/pathway and deducing the potential function of a novel gene. The validity of the predictions from the database was demonstrated with two examples through spatiotemporal analyses of the two novel genes. Such a database should serve as a highly valuable resource for the molecular analysis of human development and pathogenesis.

The mammalian gene ZNF268 is regulated by hUpf1

Nonsense-mediated mRNA decay (NMD), also called RNA surveillance, is a process that degrades mRNAs with premature translation termination codons. In Saccharomyces cerevisiae, it has also been shown that NMD can regulate gene expression at the transcriptional level. To date, there has been no example where promoters are regulated by the NMD pathway in higher eukaryotes. Taking advantage of our previous research on ZNF268 transcription control, we studied the relationship between the ZNF268 promoter and the NMD pathway. We showed by transient transfection that the ZNF268 promoter activity was influenced by hUpf1, not hSmg6, in HeLa cells. This result was confirmed by the analysis of the steady state mRNA of ZNF268 after depletion of endogenous hUpf1 or hSmg6 in HeLa cells. Direct mutational analysis revealed that the C/EBP site in the promoter region is important for hUpf1 function on ZNF268 promoter. Together our results demonstrated that the mammalian gene ZNF268 is regulated by hUpf1 via its promoter.

Human T-cell leukemia virus type 1 oncoprotein tax represses ZNF268 expression through the cAMP-responsive element-binding protein/activating transcription factor pathway

Expression of the human T-cell leukemia virus type 1 (HTLV-1) oncoprotein Tax is correlated with cellular transformation, contributing to the development of adult T-cell leukemia. In this study, we investigated the role of Tax in the regulation of the ZNF268 gene, which plays a role in the differentiation of blood cells and the pathogenesis of leukemia. We demonstrated that ZNF268 mRNA was repressed in HTLV-1-infected cells. We also showed that stable and transient expression of HTLV-1 Tax led to repression of ZNF268. In addition, by using reporter constructs that bear the human ZNF268 promoter and its mutants, we showed that Tax repressed ZNF268 promoter in a process dependent on a functional cAMP-responsive element. By using Tax, cAMP-responsive element-binding protein (CREB)-1, CREB-2, and their mutants, we further showed that Tax repressed ZNF268 through the CREB/activating transcription factor pathway. Electrophoretic mobility shift assays and chromatin immunoprecipitation demonstrated the formation of the complex of Tax.CREB-1 directly at the cAMP-responsive element both in vitro and in vivo. These findings suggest a role for ZNF268 in aberrant T-cell proliferation observed in HTLV-1-associated diseases.