Human β-interferon gene expression is regulated by an inducible enhancer element (original) (raw)
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Journal of Interferon & Cytokine Research, 1996
This paper addresses the role of transcriptional regulation in the determination of the levels of expression of dif¬ ferent interferon-subtypes secreted from Namalwa cells following infection with Sendai virus. Using RT-PCR to determine the relative abundance of mRNA species coding for the various subtypes, we found a general corre¬ lation with corresponding protein levels, indicative of a role for transcriptional control in the determination of levels of individual subtypes. We have used reporter gene constructs to compare the inducibility of the virus-re¬ sponse elements from the IFNA1, A2, A4, and A14 subtype genes cloned upstream of a secreted alkaline phos¬ phatase gene. The inducibility of these reporter gene constructs broadly correlated with the relative mRNA abundances in both transiently and stably transfected Namalwa cells. During work with stable cell lines, we found that G418, the drug used for the selection of transfected cells, inhibited the induction of interferon by both Sendai virus and double-stranded RNA. This inhibition was reversible when G418 was removed from the medium 24 h before the addition of virus.
Cell, 1986
We have used a DNAase I genomic footprinting procedure to detect interactions between cellular factors and the regulatory sequences of the human p-interferon gene. Prior to induction with poly(l)-poly(C), factors that bind to DNA are detected in one region located between-94 and-167 from the mRNA cap site, and in another region located between-68 and-38. After induction these factors dissociate and another factor binds to a region located between-77 and-64. Correlation of these footprints with the effects of deletions in the regulatory region of the p-interferon gene (accompanyin$ paper) suggest that the factors that bind prior to induction are repressor molecules, while the component that binds after induction is a transcription factor. Dissociation of the repressor molecules from the DNA after induction may allow the transcription factor to bind to and activate the p-interferon promoter. Thus, the p-interferon gene may be controller by a negative regulatory mechanism.
Molecular and Cellular Biology, 1993
We have cloned and functionally characterized the human interferon regulatory factor 1 (IRF-1) gene promoter. The promoter contains a CpG island, with several GC boxes, a CAAT box, but no TATA box. IRF-1 mRNA is strongly induced by gamma interferon (IFN-gamma) but more weakly and transiently by IFN-alpha. There are several putative kappa B motifs and numerous AA(G/A)G(G/T)A and GAAANN motifs throughout the promoter. The IRF-1 promoter is not autoregulated by the IRF-1 gene product. IFN inducibility of the promoter was studied with 5' deletion mutants linked to a heterologous reporter gene. Gel mobility shift assays were used to show IFN-inducible factor binding to the IRF-1 promoter. These studies showed that IFN inducibility is conferred by a novel imperfect inverted-repeat arrangement of two GAAANN motifs within a domain, 130 nucleotides upstream of transcription initiation. This inverted repeat binds a factor upon induction with IFN and can confer IFN inducibility on a hetero...
European Journal of Biochemistry, 1996
Type-I interferons are encoded by a multigene family, the major members of which are at least 13 IFN A subtypes and a single IFN B gene. IFNs A and B are induced in response to similar stimuli, such as virus infection and double-stranded RNA, but in different cell types: the induction of IFN A is almost exclusively restricted to cells of lymphoid origin, while IFN B has been found to be induced in a variety of cell types including fibroblasts. The virus-responsive enhancer element in the promoter region of IFN A family members is largely responsible for the differential expression of individual subtypes in responsive cells. In this paper we describe experiments which address the issue of the differential expression of IFN A and IFN B in different cell types. We show that IFN-P is induced in a variety of cells of different origin, while not all of these are able to secrete IFN-a. By transfection of reporter gene constructs comprising the virus-responsive enhancer from the IFN A1 and IFN B genes, we show that this differential response is mediated at the level of transcription via these control elements. More detailed analysis of the function of these regions identifies specific sequences within the IFN A1 virus response element that has an inhibitory effect on expression in cells that are normally inducible, and is also implicated in the overall suppression of IFN A induction in non-inducible cells.
Two levels of regulation of beta-interferon gene expression in human cells
Proceedings of the National Academy of Sciences, 1983
We cloned alpha- and beta-interferon cDNA and used them as specific probes to determine the relative levels of interferon mRNA in human fibroblasts cells induced with poly(rI).poly(rC) or Newcastle disease virus to synthesize interferon. Both inducers activated only the beta-interferon gene; however, the half life of beta-interferon mRNA in cells induced with virus was substantially longer than in poly(rI).poly(rC)-induced cells. The transcription rate of beta-interferon RNA sequences was examined in nuclei isolated from poly(rI).poly(rC)-induced cells; it was found that the induction leads to transcriptional activation of the beta-interferon gene and that the shutoff period when no interferon synthesis or cytoplasmic betamRNA are detected. Thus, the synthesis of beta interferon in poly(rI).poly-(rC)-induced human fibroblasts is controlled both by activation of transcription of the beta-interferon gene and by alteration of the beta-interferon mRNA stability.
The Journal of biological chemistry, 1994
Interferon (IFN) regulatory factor 1 (IRF-1) and IRF-2 are structurally similar but functionally distinct transcription factors that bind to the positive regulatory domains I and III (PRDI/III) within the human IFN-beta promoter. To begin structure-function analysis of IRF-1 and IRF-2, the regulatory potential of carboxyl-terminal deletion mutants was analyzed by co-transfection studies in human cells and was correlated with DNA binding capacity. Transcriptional repression by IRF-2 was contained within the first 125 amino-terminal amino acids and correlated directly with IRF-2 DNA binding; deletion to a protein of 100 amino acids resulted in loss of repression and IRF-2 DNA binding. Thus, the carboxyl terminus appears dispensible for trans-repression. Hybrid constructs which fuse the DNA binding domain of IRF-1 and IRF-2 to the trans-activation domain of NF-kappa B p65 were also generated; both IRF-1/p65 and IRF-2/p65 chimeras were strong transcriptional activators. IRF-2-mediated r...
Molecular mechanisms of interferon beta gene induction
Seminars in Virology, 1995
The Type 1 interferon genes (IFNA and IFNB) have served as an important paradigm to examine the mechanisms of virus inducible gene expression. In particular, IFNB has been amenable to reverse genetic approaches for the analysis of transcriptional activation. The DNA sequences that regulate IFNB gene transcription are located within a 110 nucleotide region, immediately upstream of the structural gene and consist of multiple, overlapping positive and negative regulatory domains essential for virus-induced activation and/or repression of the promoter. The positive regulatory domains I and III (PRDI and PRDIII)
Journal of Virology, 2002
functions as a key activator of the immediate-early alpha/beta interferon (IFN) genes, as well as the RANTES chemokine gene. In the present study, a tetracycline-inducible expression system expressing a constitutively active form of IRF-3 (IRF-3 5D) was combined with DNA microarray analysis to identify target genes regulated by IRF-3. Changes in mRNA expression profiles of 8,556 genes were monitored after Tet-inducible expression of IRF-3 5D. Among the genes upregulated by IRF-3 were transcripts for several known IFN-stimulated genes (ISGs). Subsequent analysis revealed that IRF-3 directly induced the expression of ISG56 in an IFN-independent manner through the IFN-stimulated responsive elements (ISREs) of the ISG56 promoter. These results demonstrate that, in addition to its role in the formation of a functional immediate-early IFN- enhanceosome, IRF-3 is able to discriminate among ISRE-containing genes involved in the establishment of the antiviral state as a direct response to virus infection.
The Journal of biological chemistry, 2000
The molecular mechanism by which virus induces expression of the early inflammatory genes has not yet been completely elucidated. Previous studies indicated that the virus-mediated transcription of type I interferon (IFN) genes required activation of two members of IFN regulatory factor (IRF) family, IRF-3 and IRF-7, where the expression of IRF-7 was found to be indispensable for the induction of IFNA genes. To determine the factors that regulate expression of IRF-7 gene, as well as its inducibility by type I IFNs, we have isolated and characterized the promoter and first intron of the human IRF-7 gene. This region shows a presence of two potential interferon-sensitive response elements (ISRE/IRF-E). However, only the ISRE present in the first intron was functional and conferred interferon inducibility in a transient transfection assay. Using a pull-down assay with an oligodeoxynucleotide corresponding to this ISRE immobilized to magnetic beads, we have demonstrated that this ISRE b...
Proceedings of the National Academy of Sciences, 1998
The family of interferon (IFN) regulatory factors (IRFs) encodes DNA-binding transcription factors, some of which function as modulators of virus-induced signaling. The IRF-3 gene is constitutively expressed in many tissues and cell types, and neither virus infection nor IFN treatment enhances its transcription. In infected cells, however, IRF-3 protein is phosphorylated at the carboxyl terminus, which facilitates its binding to the CBP͞p300 coactivator.