Role Of IRF-1 Research Articles

A ChIP–chip approach reveals a novel role for transcription factor IRF1 in the DNA damage response

IRF1 is a transcription factor that regulates key processes in the immune system and in tumour suppression. To gain further insight into IRF1's role in these processes, we searched for new target genes by performing chromatin immunoprecipitation coupled to a CpG island microarray (ChIP–chip). Using this approach we identified 202 new IRF1-binding sites with high confidence. Functional categorization of the target genes revealed a surprising cadre of new roles that can be linked to IRF1. One of the major functional categories was the DNA damage response pathway. In order to further validate our findings, we show that IRF1 can regulate the mRNA expression of a number of the DNA damage response genes in our list. In particular, we demonstrate that the mRNA and protein levels of the DNA repair protein BRIP1 [Fanconi anemia gene J (FANC J)] are upregulated after IRF1 over-expression. We also demonstrate that knockdown of IRF1 by siRNA results in loss of BRIP1 expression, abrogation of BRIP1 foci after DNA interstrand crosslink (ICL) damage and hypersensitivity to the DNA crosslinking agent, melphalan; a characteristic phenotype of FANC J cells. Taken together, our data provides a more complete understanding of the regulatory networks controlled by IRF1 and reveals a novel role for IRF1 in regulating the ICL DNA damage response.

5 The role of IRF-5 in the antiviral and inflammatory response

5 The role of IRF-5 in the antiviral and inflammatory response

The genetics and biology of Irf5-mediated signaling in lupus

Recently much attention was attracted to the importance of the type I interferon pathway in the initiation and development of the autoimmune disease systemic lupus erythematosus (SLE). Many SLE patients have increased serum levels of IFN-α and display an IFN gene expression “signature” characterized by strong overexpression of IFN-responsive genes in leukocytes and target tissues. Moreover, about 20% of cancer patients treated with IFN-α therapy manifest symptoms resembling SLE and some later develop the disease. One of the key genes of the IFN-α pathway, IRF5, was found to be strongly associated with SLE. Two functional SNPs lead to alternative splicing and altered steady-state level of IRF5 gene expression. Besides, the gene has a polymorphic inserion/deletion in exon 6, which contributes to the diversity in the isoform pattern of IRF5. Interestingly, recent studies have not found association of IRF5 with the other autoimmune diseases, such as rheumatoid arthritis or psoriasis, suggesting the unique role for IRF5 in the development of lupus. Here, we present the current knowledge on IRF5 genetics and its biological function and discuss the possible ways in which IRF5 contributes to susceptibility to SLE.

Interferon Regulatory Factor 8 Regulates RANTES Gene Transcription in Cooperation with Interferon Regulatory Factor-1, NF-κB, and PU.1

Interferon regulatory factor (IRF)-8 is a member of the IRF family of transcription factors important in interferon-gamma-mediated signaling and in the development and function of dendritic cells. Regulated on activation, normal T cell expressed and secreted (RANTES, or CCL5) is a member of the CC chemokine family of proteins, strongly chemoattractant for several important immune cell types in host defense against infectious agents and cancer. Here we report that RANTES expression in IRF-8-null macrophages stimulated with interferon-gamma and lipopolysaccharide is markedly decreased. IRF-8 can activate RANTES gene transcription in synergism with IRF-1. Interestingly, IRF-8 can activate RANTES transcription independently of IRF-1 through direct physical interactions with NF-kappaB c-Rel and PU.1 via the NF-kappaB element located at -88 to -79 in vitro and in vivo. This study uncovers a novel role of IRF-8 in the regulation of RANTES gene expression and the underlying molecular mechanisms whereby IRF-8 interacts with several other important transcription factors to initiate innate immune responses to pathogenic and inflammatory challenges by activating the RANTES gene.

857 IFN-γ/STAT1 acts as a pro-inflammatory signal in T cell-mediated hepatitis via induction of multiple chemokines and adhesion molecules: a critical role of IRF-1

857 IFN-γ/STAT1 acts as a pro-inflammatory signal in T cell-mediated hepatitis via induction of multiple chemokines and adhesion molecules: a critical role of IRF-1

Transcription factor IRF-1 in kidney transplants mediates resistance to graft necrosis during rejection.

In many circumstances kidney transplants remain viable despite extensive inflammation, permitting rejection episodes to be reversed. The mechanisms by which the kidney resists host effector mechanisms are not known. In mouse kidney transplants, resistance requires interferon-gamma (IFN-gamma), which acts on the graft to protect the graft from necrosis during the first days of rejection as well as inducing major histocompatibility complex (MHC) expression. Because some effects of IFN-gamma are mediated by transcription factor IRF-1, the role of IRF-1 in the donor tissue early phases of rejection of mouse kidney allografts was studied. H-2(b) kidneys were transplanted from mice with wild-type IRF-1 genes (WT) or mice with disrupted IRF-1 genes (IRF-1KO) into CBA (H-2(k)) recipients. At day 5 and day 7, IRF-1KO and WT kidneys were functioning despite typical rejection pathology: interstitial infiltration and tubulitis. However, function deteriorated rapidly in rejecting IRF-1KO allografts, associated with widespread epithelial necrosis, peritubular capillary congestion, glomerulitis, and fibrin thrombi in small veins by day 7. At day 21, WT kidneys were viable despite severe tubulitis and arteritis, whereas IRF-1KO kidneys showed massive necrosis of the epithelium despite patent large vessels. Compared with WT kidneys, rejecting IRF-1KO kidneys showed less induction of donor MHC yet had similar mRNA levels of perforin, granzyme B, and Fas ligand and evoked host alloantibody responses. Thus in rejecting kidney transplants, IRF-1 in the graft mediates MHC induction, but it also mediates resistance to necrosis, an effect that could be crucial to permit success in interventions against rejection.

856. The Role of IRF-1 in Immune-Mediated Clearance ofAdenovirus Vector

856. The Role of IRF-1 in Immune-Mediated Clearance ofAdenovirus Vector

The role of IRF-4 in transcriptional regulation.

Gene expression is a tightly regulated process involving multiple levels of control spanning histone acetylation to protein turnover. One of the first events in this cascade is transcription, which itself is a multistep process involving protein-protein interaction and macromolecular assembly. Here we review the role of the interferon (IFN) regulatory factor (IRF) transcription factor family member IRF-4 in transcriptional regulation. IRF-4 was initially characterized in lymphocytes and was shown to function as both a transcriptional repressor and activator. More recently, IRF-4 expression and function have been reported in macrophages. The ability of IRF-4 to serve as both a transcriptional activator and repressor is determined, in part, by binding to distinct DNA-binding motifs and through interaction with various additional transcription factors, most notably with the Ets family member PU.1. The details governing these functional differences are the focus of this review. Importantly, the role of posttranslational modification and nuclear translocation of IRF-4 in transcriptional regulation are addressed. Several possible paradigms of transcriptional regulation by IRF-4 are proposed, where these paradigms may describe regulatory mechanisms common to many distinct transcription factor families.

Interferon Regulatory Factors: Bridging Antiviral Defense, Growth Control, and Immunoregulation

3 SINCE THEIR DISCOVERY IN 1957, interferons (IFN) have continuously played a central role in basic, applied, and clinical research as mediators of antiviral and antigrowth responses, as modulators of the immune response, and as therapeutic agents to combat viral diseases and cancer. IFN have served also as an important paradigm to investigate cytokine responses, signal transduction, and transcription control. Much of the information available on IFN gene regulation has derived from studies on the family of type I IFN genes, as well as the IFNstimulated genes (ISG), and has resulted in characterization of novel transcriptional proteins, common and unique signalling pathways leading to IFN and ISG activation, and the discovery of the IFN regulatory factors (IRF) and signal transducers and activators of transcription (Stat) families. IRF-1 and IRF-2 were originally identified as the transcriptional activator and repressor, respectively, of the type I IFN genes. The family has now expanded to include seven additional members: IRF-3 IRF-4 (Pip/LSIRF/ICSAT), IRF-5, IRF-6, IRF-7, IRF-8 (IFN consensus sequence binding protein [ICSBP]), and IRF-9 (ISG factor 3g/p48 [ISGF3g/p48]), and with the expansion has come the recognition of essential roles of IRF in immune regulation, growth control, and hematopoietic differentiation. All IRF share a high degree of homology in the N-terminal DNA binding domain and generally bind the DNA sequence GAAANNGAAANN. Variations in this canonical sequence, together with IRF interactions with other transcriptional partners, lead to the generation of transactivation and in some cases transrepression potential. Additional mechanisms allowing for differential gene regulation by IRF include cell type specificity, subcellular localization, and activator-specific phosphorylation events. The C-terminal portion of the IRF proteins is unique to each member and also contributes to the functional diversification of the IRF. The presence of virally encoded versions of IRF (vIRF) in the genome of human herpesvirus-8 (HHV-8), the virus responsible for Kaposi’s sarcoma, also illustrates the fact that viruses have evolved numerous mechanisms to evade the antiviral effect of IFN, including strategies to target the IRF. This Special Issue of the Journal of Interferon and Cytokine Research brings together many of the world’s leading researchers on this subject, and together they provide a comprehensive view of the range of activities controlled by the IRF family members. B. Barnes and colleagues provide an overview of the functions of the IRF in the innate immune response and immune evasive tactics of the vIRF homologs. Hauser’s group and Romeo’s group discuss the antiproliferative and tumorsuppressive properties of IRF-1. A. Battistini and colleagues describe the role of IRF-1 in regulating transcription from the HIV-1 long terminal repeat, and R. Pine illustrates a role for the IRF in the host response to mycobacterial infection. IRF-3 and IRF-7 are specifically involved in type I IFN gene expression. Viral infection causes the activation of an unknown kinase(s) and phosphorylation of both IRF-3 and IRF-7 in the cytoplasm. Virus-activated IRF-3/IRF-7 may undergo a conformational change that allows specific DNA binding to the type I IFN promoters, coactivator recruitment, and transcription of target genes. Several reviews cover this active area of research. M. Servant and colleagues discuss the structure and functional activation of IRF-3 and IRF-7. Fujita’s group provides a view of the regulatory phosphorylation events responsible for IRF-3 induction, and N.C. Reich reviews her studies on the mechanisms of nuclear import and export of IRF-3. Structure-function studies on the related IRF-7 factor are described by D. Levy and colleagues; L. Zhang and J.S. Pagano contribute a distinct view of IRF-7 from the perspective of the involvement of IRF-7 in control of Epstein-Barr virus transcription. A. Civas’s group describes the interactions of IRF-3 and IRF-7 with the IFN-a promoters. The lymphoid-myeloid-restricted members of the IRF family are also reviewed. S. Marecki and M. Fenton analyze the structure and function of IRF-4, with emphasis on the role of IRF-4 in macrophage-specific gene regulation, and A. Pernis addresses the functions of IRF-4 in T and B lymphoid cellspecific gene expression. From a different viewpoint, Y. Mamane and colleagues focus on the consequences of IRF-4 constitutive activation in human T cell leukemia virus (HTLV-1)infected lymphoid cells. T. Tamura and K. Ozato review their studies on the role of IRF-8/ICSBP in myeloid differentiation and the regulation of myeloid-specific target genes by IRF-8. B.-Z. Levi and colleagues review the functional protein-protein

The role of irf-1 and caspase-7 in ifn-gamma enhancement ofFAS-mediated apoptosis in achn renal cell carcinoma cells

The role of irf-1 and caspase-7 in ifn-gamma enhancement ofFAS-mediated apoptosis in achn renal cell carcinoma cells

Downregulation of IRF-3 levels by ribozyme modulates the profile of IFNA subtypes expressed in infected human cells.

As an early response to viral infection, cells express a number of cellular genes that play a role in innate immunity, including alpha/beta interferons (IFN). IFN-alpha/beta are encoded by a single IFNB gene and multiple, closely related IFNA genes. The induction of these IFN genes in infected cells occurs at the transcriptional level, and two transcription factors of the IRF family, IRF-3 and IRF-7, were shown to play a role in their activation. While the expression of IRF-3 alone was shown to be sufficient for induction of the IFNB gene, induction of all the IFNA subtypes in human cells required the presence of IRF-7. Since IRF-3 is expressed constitutively in all cells examined, the role of IRF-3 in the induction of IFNA genes has not been clarified. Using ribozyme targeted to IRF-3 mRNA, we found that the downregulation of IRF-3 levels in the infected cells inhibited not only the induction of IFNB gene but also the expression of IFNA genes. Furthermore, downmodulation of IRF-3 levels altered the expression profile of IFNA subtypes induced by viral infection. These studies suggest that the ratio between the relative levels of IRF-3 and IRF-7 is a critical determinant for the induction of the individual IFNA subtypes in infected cells.

A novel role for IRF-1 as a suppressor of apoptosis.

The tumour suppressor IRF-1 is a transcription factor involved in the induction of apoptosis in several in vitro systems. Post-lactational involution of the mammary gland is characterized by extensive apoptosis of the epithelial cells. We have previously shown that signal transducer and activator of transcription (Stat) 3 drives apoptosis and involution in the mouse mammary gland. Since one of the downstream targets of the Stat signalling pathway is IRF-1, we have used IRF-1 knockout mice to address the potential role of this transcription factor in involution. Surprisingly, in the absence of IRF-1 significantly higher numbers of apoptotic cells were found in involuting glands at 48 h compared to control glands. In addition, the alveolar structure in IRF-1 null mammary glands had collapsed whereas in control glands the alveoli remained intact and distended. However, by 72 h control and null glands were morphologically similar suggesting that IRF-1 suppresses apoptosis only during the early, reversible, stage of involution. This suggests a survival role for IRF-1 in mammary epithelia and demonstrates a novel role for IRF-1 in vivo--suppression of premature epithelial apoptosis during mammary gland involution.

Identification of the secretory leukocyte protease inhibitor (SLPI) as a target of IRF-1 regulation.

Interferon Regulatory Factor (IRF)-1 is a multifunctional transcription factor, involved in cell growth regulation, pathogen response and immune activation. To identify novel gene targets that may contribute to IRF-1 mediated activities, RNA fingerprinting was performed using NIH3T3 cells that inducibly express a hybrid form of IRF-1 under tetracycline regulated control. Secretory leukocyte protease inhibitor (SLPI) - a regulator of inflammation and an inhibitor of the LPS response - was identified as a gene repressed after doxycycline induced IRF-1 expression. Preliminary analysis of the human SLPI promoter identified an ISRE-like site located within the -221 to -200 region to which IRF-1 binds and a second, putative IRF-1 binding site upstream of the TATA box. Furthermore, co-transfection studies demonstrated that SLPI expression was inhibited by IRF-1 co-expression. The identification of SLPI as a target of IRF-1 regulation reveals a unique involvement of IRF-1 in repression of gene transcription and assigns a novel role for IRF-1 in inflammation.

Type I interferon gene expression: Differential expression of IFN-A genes induced by viruses and double-stranded RNA

The family of interferon regulatory transcription factors (IRF) participates in the virus-induced and dsRNA-stimulated transcriptional regulation of either type I IFN genes or a definite set of genes which can also be activated by IFN. In this review, we place emphasis on the role of IRF-3 that associates with the coactivators CBP and/or p300, together or not with IRF-7. These complexes bind to the PRDI, PRDI-like domains or to a number of ISRE sequences located in the promoter of these virus-inducible genes. We also discuss the involvement of the IRF-3-related complexes in the differential regulation of IFN-A genes.

Regulation of LMP2 and TAP1 Genes by IRF-1 Explains the Paucity of CD8 + T Cells in IRF-1 −/− Mice

The TAP1 and LMP2 genes are central for class I MHC function and share a common promoter. Here, we analyze the molecular mechanism of IFNγ up-regulation of TAP1 and LMP2. In vivo footprinting indicates IFNγ up-regulates protein–DNA contacts at an IRF-E that is essential for the up-regulation of TAP1 and LMP2 by IFNγ. Gel shift analysis indicates that this site binds IRF-1. The expression of TAP1 and LMP2 are both greatly reduced in IRF-1-deficient mice. Surface class I MHC as well as CD8 + T cells are reduced in IRF-1 −/− mice. The role of IRF-1 in the regulation of TAP1 and LMP2 suggests a mechanism for the antiviral properties of IRF-1 and the unexpected deficiency of CD8 + T cells observed in IRF-1 −/− mice.