resence of hypoxia rely on the increased promoter activity and are not due to resistance to IKK-mediated accelerated proteolytic degradation. Induction of ZNF395 by hypoxia might thus give rise to a transcriptional active protein. Discussion A gene expression array revealed that the genes whose expression was induced by the hypoxia-inducible factor ZNF395 are part of pathways involved in cancer and in the innate immune response. SiRNA-based knockdown confirmed that endogenous ZNF395 expressed in U87-MG cells and in the keratinocyte cell line RTS3b contributes to the basal transcription of ISG56 and IFI44, since their expression declines in the presence of siRNA targeting ZNF395 in contrast to the control siRNA, confirming the PG-490 manufacturer specificity. Most importantly, knockdown of ZNF395 considerably impaired the IFN–mediated stimulation of ISG56, IFI44 and IFI16 in the keratinocyte cell line. Although the overall effects, i.e. the induction by IFN- and impairment due to loss of ZNF395, were less dramatic in U87-MG cells, our results strongly support the notion that ZNF395 is a novel factor modulating the activation of these factors within the first innate immune response upon virus infection. It is well known that ISG56 contributes to establish an antiviral state via multiple effects on viral and cellular functions such as inhibition of translation, viral replication and cell proliferation. IFI44 was shown to have antiviral activity against HCV as well as anti-proliferative activities. IFI16 acts as an intracellular sensor of dsDNA, including viral DNAs to induce an innate immune response. A role of ZNF395 in the innate immune response against virus infections is supported by several reports. Genome-wide screens found transcripts for ZNF395 reduced in CD8+ T-cells 25090924 from HIV viremic 1659286 patients compared to CD8+ T lymphocytes from uninfected or HIV-infected therapy-nave long-term non-progressors. Similarly, ZNF395 expression was downregulated in CD8+ T lymphocytes in the acute phase of HCMV infection compared to nave CD8+ T-cells. Thus, CMV or HIV viral replication might be more efficient at low ZNF395 concentration. A recent study showed that IFI16 Hypoxia induces the expression of ZNF395, which is transcriptionally active We considered analyzing the phosphorylation status of endogenous ZNF395, but we were unable to detect endogenous ZNF395 in various cell lines, which may be due to the IKK-mediated degradation of the protein. As already mentioned, data from the literature suggested that ZNF395 is a hypoxia-induced gene. We performed qRT-PCR with RNA from U87-MG and U937 cells, which were grown for 12h in 2% O2 atmosphere, and found a 5.3- and 1.7-fold increase of ZNF395 expression due to hypoxia, respectively. In correlation, endogenous ZNF395 became detectable by IB with protein extracts from these cells when they were incubated in 2% O2 atmosphere. To address a post-translational modification of endogenous ZNF395 by IKK, we tested whether BMS-345541, i.e. inhibition of IKK affects the migration of endogenous ZNF395 induced by hypoxia. U87-MG cells were incubated for 12h at 2% O2 atmosphere in the presence or absence of BMS-345541. As shown in 10 ZNF395 as Modulator of ISG Transcription doi: 10.1371/journal.pone.0074911.g005 11 ZNF395 as Modulator of ISG Transcription doi: 10.1371/journal.pone.0074911.g006 acts as a restriction factor for HCMV replication. According to our data, low levels of ZNF395 will result in a reduced IFN-dependent induction o

Data extraction and quality assessment Data were collected independently by 2 reviewers

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