The POU transcription factor Oct-1 represses virus-induced interferon A gene expression

Bovine Transcription Factor POU Class 2 Homeobox 1 (POU2F1/Oct1) Protein Promotes BoHV-1 Replication in MDBK Cells

Bovine herpesvirus type 1 (BoHV-1) causes severe diseases in bovine species and great economic burden to the cattle industry worldwide. Due to its complex life cycle, many host factors that affect BoHV-1 replication remain to be explored. To understand the possible roles that the Oct1 cellular protein could play in this process, we first created Oct1-deficient MDBK cells using CRISPR/Cas9-mediated genome editing. Upon infection, the absence of Oct1 in MDBK cells significantly impacted BoHV-1 replication, a phenotype rescued by over-expressing the wild-type Oct1 protein in the deficient cells. We further found that the expression of all three classes of temporal genes, including essential and non-essential viral genes, were significantly reduced in Oct1 knockout MDBK cells, following both high and low multiplicity of infection. In summary, our findings confirm that the bovine Oct1 protein acts as a pro-viral factor for BoHV-1 replication by promoting its viral gene transcription in MDBK cells.

Differential activity of interferon-α8 promoter is regulated by Oct-1 and a SNP that dictates prognosis of glioma

We have previously reported that the single nucleotide polymorphism (SNP) rs12553612 in IFNA8 is associated with better overall survival of glioma patients with the AA-genotype compared with patients with the AC-genotype. As rs12553612 is located in the IFNA8 promoter, we hypothesized that the A-allele allows for an enhanced IFNA8 promoter activity compared with the C-allele. Reporter assays in the human monocyte derived THP-1 cell line demonstrated a superior promoter activity of the A-allele compared with the C-allele. Electrophoretic mobility shift assays (EMSA) further demonstrated that the A-genotype specifically binds to more nuclear proteins than the C-genotype, including the transcription factor Oct-1. Further, co-transfection of plasmids encoding Oct-1 and the reporter constructs revealed that Oct-1 enhanced the promoter activity with the A- but not the C-allele. Taken together, our data demonstrate that the A-allele in the rs12553612 SNP, which is associated with better glioma patient survival, allows for IFNA8 transcription by allowing for Oct-1 binding, which is absent in patients with C allele, and suggests a molecular mechanism of IFNA8 mediated immune-surveillance of glioma progression.

An invertebrate signal transducer and activator of transcription 5 (STAT5) ortholog from the disk abalone, Haliotis discus discus: Genomic structure, early developmental expression, and immune responses to bacterial and viral stresses

Signal transducer and activator of transcription (STAT) family members are key signaling molecules that transduce cellular responses from the cell membrane to the nucleus upon Janus kinase (JAK) activation. Although seven STAT members have been reported in mammals, very limited information on STAT genes in molluscans is available. In this study, we identified and characterized a STAT paralog that is homologous to STAT5 from the disk abalone, Haliotis discus discus, and designated as AbSTAT5. Comparison of the deduced amino acid sequence for AbSTAT5 (790 amino acids) with other counterparts revealed conserved residues important for functions and typical domain regions, including the N-terminal domain, coiled-coil domain, DNA-binding domain, linker domain, and Src homology 2 (SH2) domains as mammalian counterparts. Analysis of STAT phylogeny revealed that AbSTAT5 was clustered with the molluscan subgroup in STAT5 clade with distinct evolution. According to the genomic structure of AbSTAT5, the coding sequence was distributed into 20 exons with 19 introns. Immunologically essential transcription factor-binding sites, such as GATA-1, HNF, SP1, C/EBP, Oct-1, AP1, c-Jun, and Sox-2, were predicted at the 5'-proximal region of AbSTAT5. Expression of AbSTAT5 mRNA was detected in different stages of embryonic development and observed at considerably higher levels in the morula and late veliger stages. Tissue-specific expressional studies revealed that the highest level of AbSTAT5 transcripts was detected in hemocytes, followed by gill tissues. Temporal expressions of AbSTAT5 were analyzed upon live bacterial (Vibrio parahemolyticus and Listeria monocytogenes), viral (viral hemorrhagic septicemia virus), and pathogen-associated molecular pattern (lipopolysaccharides and Poly I:C) stimulations, and significant elevations indicated immune modulation. These results suggest that AbSTAT5 may be involved in maintaining innate immune responses from developmental to adult stages in the disk abalone. Further, this study provides a basis for structural and functional exploration of STAT members in the invertebrate JAK/STAT signaling pathway.

Sequence analysis, expression patterns and transcriptional regulation of mouse Ifrg15 during preimplantation embryonic development

Ifrg15 is a newly identified interferon alpha responsive gene and is implicated in a wide variety of physiological roles in mammals. In the present study, multiple alignments of the deduced amino acids of 10 eutherian mammalian IFRG15/Ifrg15s isolated from open genomic database revealed that they were highly conserved. Real-time PCR showed that mouse Ifrg15 mRNA was expressed in MII stage oocytes and preimplantation embryos, and its highest value peaked at the stage of mouse blastocysts. To understand the effect of three development-related genes on the promoter activity of mouse Ifrg15, promoter analysis using luciferase assays in COS-7 cells were performed. The results showed that the transcription of mouse Ifrg15 was suppressed by Oct4 and Nanog when transfected with the longest Ifrg15 promoter reporter gene. After the relatively shorter promoters were co-transfected with Oct4, c-Myc and Nanog, the relative luciferase activities of Ifrg15 were gradually increased. These in vitro results data and expression profiles of Ifrg15 as revealed by real-time PCR partly indicated that Ifrg15 transcription might be either potentially regulated or dependent on the post-transcriptional effects of IFN-α mediated by the three genes indirectly. Our data suggested that the mouse Ifrg15 might interact with these key development-related genes and play significant roles on the mouse preimplantation embryos development, especially for the development of mouse blastocysts.

An interferon-related signature in the transcriptional core response of human macrophages to Mycobacterium tuberculosis infection

The W-Beijing family of Mycobacterium tuberculosis (Mtb) strains is known for its high-prevalence and -virulence, as well as for its genetic diversity, as recently reported by our laboratories and others. However, little is known about how the immune system responds to these strains. To explore this issue, here we used reverse engineering and genome-wide expression profiling of human macrophage-like THP-1 cells infected by different Mtb strains of the W-Beijing family, as well as by the reference laboratory strain H37Rv. Detailed data mining revealed that host cell transcriptome responses to H37Rv and to different strains of the W-Beijing family are similar and overwhelmingly induced during Mtb infections, collectively typifying a robust gene expression signature (“THP1r2Mtb-induced signature”). Analysis of the putative transcription factor binding sites in promoter regions of genes in this signature identified several key regulators, namely STATs, IRF-1, IRF-7, and Oct-1, commonly involved in interferon-related immune responses. The THP1r2Mtb-induced signature appeared to be highly relevant to the interferon-inducible signature recently reported in active pulmonary tuberculosis patients, as revealed by cross-signature and cross-module comparisons. Further analysis of the publicly available transcriptome data from human patients showed that the signature appears to be relevant to active pulmonary tuberculosis patients and their clinical therapy, and be tuberculosis specific. Thus, our results provide an additional layer of information at the transcriptome level on mechanisms involved in host macrophage response to Mtb, which may also implicate the robustness of the cellular defense system that can effectively fight against genetic heterogeneity in this pathogen.

Octamer-binding factor 6 (Oct-6/Pou3f1) is induced by interferon and contributes to dsRNA-mediated transcriptional responses

BACKGROUND

Octamer-binding factor 6 (Oct-6, Pou3f1, SCIP, Tst-1) is a transcription factor of the Pit-Oct-Unc (POU) family. POU proteins regulate key developmental processes and have been identified from a diverse range of species. Oct-6 expression is described to be confined to the developing brain, Schwann cells, oligodendrocyte precursors, testes, and skin. Its function is primarily characterised in Schwann cells, where it is required for correctly timed transition to the myelinating state. In the present study, we report that Oct-6 is an interferon (IFN)-inducible protein and show for the first time expression in murine fibroblasts and macrophages.

RESULTS

Oct-6 was induced by type I and type II IFN, but not by interleukin-6. Induction of Oct-6 after IFNbeta treatment was mainly dependent on signal transducer and activator of transcription 1 (Stat1) and partially on tyrosine kinase 2 (Tyk2). Chromatin immunopreciptitation experiments revealed binding of Stat1 to the Oct-6 promoter in a region around 500 bp upstream of the transcription start site, a region different from the downstream regulatory element involved in Schwann cell-specific Oct-6 expression. Oct-6 was also induced by dsRNA treatment and during viral infections, in both cases via autocrine/paracrine actions of IFNalpha/beta. Using microarray and RT-qPCR, we furthermore show that Oct-6 is involved in the regulation of transcriptional responses to dsRNA, in particular in the gene regulation of serine/threonine protein kinase 40 (Stk40) and U7 snRNA-associated Sm-like protein Lsm10 (Lsm10).

CONCLUSION

Our data show that Oct-6 expression is not as restricted as previously assumed. Induction of Oct-6 by IFNs and viruses in at least two different cell types, and involvement of Oct-6 in gene regulation after dsRNA treatment, suggest novel functions of Oct-6 in innate immune responses.

Identification of a suppressor element in the amelogenin promoter

Amelogenin expression is regulated in a cell-type- specific manner. Investigators have previously identified an enhancer element by using the 5' flanking sequence of the amelogenin promoter. However, the cell-type-specific regulation of the amelogenin gene remains poorly understood. In some genes, the first intron regulates tissue-specific expression. We hypothesized that intron 1 is important for the cell-type-specific regulation of amelogenin expression. We identified a suppressor element between -74 and -464. We also found enhancer activity in intron 1. Additionally, we found that the suppressor element in the promoter region suppressed intron 1 enhancer activity. The suppressor and the enhancers acted in an ameloblast-like cell line, but not in HeLa cells. Mutation of the Oct-1 binding sites reversed the suppressor activity, suggesting that Oct-1 sites are essential for suppression. These results suggest that Oct-1 and intron 1 may contribute to cell-type-specific amelogenin expression.

Adenoviral infection induces a multi-faceted innate cellular immune response that is mediated by the toll-like receptor pathway in A549 cells

Adenovirus vectors are known to induce certain genes and impact innate response networks, but a broad understanding of this process and its mechanisms is currently lacking. For this reason, we chose to investigate and characterize Ad innate immunity using homogeneous, primary MEF cells replete with all the elements of the pathogen-sensing Toll-Like Receptor (TLR) pathway. By using an array-based approach to maximally define transcriptome changes induced upon Ad vector infection, we discovered that Ad infection induces a potent gene and transcription factor network response. This response is characterized by significant changes in the expression of genes involved in focal adhesion, tight junction, and RNA regulation, in addition to TLR pathway and other innate sensing genes. Further investigation using human A549 cells knocked down for various TLR pathway adaptors, revealed significant impacts on the Ad initiation of NF-kB and interferon responses, thus confirming TLR involvement in Ad-mediated immunity across diverse species.