The Hypoxia-Inducible Transcription Factor ZNF395 Is Controlled by IĸB Kinase-Signaling and Activates Genes Involved in the Innate Immune Response and Cancer

Abstract

Activation of the hypoxia inducible transcription factor HIF and the NF-ĸB pathway promotes inflammation-mediated tumor progression. The cellular transcription factor ZNF395 has repeatedly been found overexpressed in various human cancers, particularly in response to hypoxia, implying a functional relevance. To understand the biological activity of ZNF395, we identified target genes of ZNF395 through a genome-wide expression screen. Induced ZNF395 expression led to the upregulation of genes known to play a role in cancer as well as a subset of interferon (IFN)-stimulated genes (ISG) involved in antiviral responses such as IFIT1/ISG56, IFI44 and IFI16. In cells that lack ZNF395, the IFN-α-mediated stimulation of these factors was impaired, demonstrating that ZNF395 is required for the full induction of these antiviral genes. Transient transfections revealed that ZNF395-mediated activation of the IFIT1/ISG56 promoter depends on the two IFN-stimulated response elements within the promoter and on the DNA-binding domain of ZNF395, a so-called C-clamp. We also show that IĸBα kinase (IKK)-signaling is necessary to allow ZNF395 to activate transcription and simultaneously enhances its proteolytic degradation. Thus, ZNF395 becomes activated at the level of protein modification by IKK. Moreover, we confirm that the expression of ZNF395 is induced by hypoxia. Our results characterize ZNF395 as a novel factor that contributes to the maximal stimulation of a subset of ISGs. This transcriptional activity depends on IKK signaling further supporting a role of ZNF395 in the innate immune response. Given these results it is possible that under hypoxic conditions, elevated levels of ZNF395 may support inflammation and cancer progression by activating the target genes involved in the innate immune response and cancer.

Identification of activated enhancers and linked transcription factors in breast, prostate, and kidney tumors by tracing enhancer networks using epigenetic traits

“…ZNF395 , which encodes a protein having one C2H2-type zinc finger domain, is overexpressed in various tumors including kidney cancer [22] and has been reported to be induced by hypoxia involved in IKK signaling [23]. The ZNF395 gene is located at 8p21, and TENET identified hypomethylation of enhancer probe cg12116192 (located ~500 kb from the TSS of ZNF395 ) to be positively associated with the expression of the ZNF395 gene (Fig.…”

VHL Deficiency Drives Enhancer Activation of Oncogenes in Clear Cell Renal Cell Carcinoma

“…MCF7 cells under hypoxia (but not normoxia) share similar H3K27ac profiles as 786-O (29). Although ZNF395 is highly expressed in ccRCC, its low basal expression can be upregulated upon hypoxia in other cancer types, including glioblastoma and skin cancer (104,105). Targeting ZNF395 or its downstream effectors in future studies may be therapeutically relevant to both ccRCC and other hypoxic solid malignancies.…”

“…ZNF395 has been shown to bind to the promoters of Huntington gene (101) and interferon-induced genes, and to cause upregulation of cancer-related genes (MACC1, PEG10, CALCOCO1, and MEF2C; ref. 104) and proangiogenic chemokines including IL6 and IL8 under hypoxia (105). It remains to be elucidated in future studies the precise mechanism contributing to ZNF395's tumorigenic role.…”

ZNF395 Is an Activator of a Subset of IFN-Stimulated Genes

“…48 h later the cells were harvested in 100 mM KPO 4 , pH 7.8, 0.1% NP40, and 1 mM DTT and the luciferase activity was determined with Promega's GloMax® Multi Reader as described previously [12]. RTS3b cells were transfected with the appropriate expression vectors using Fugene HD (Roche Diagnostics).…”