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Introduction: Autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis affect millions of people worldwide. Interferon regulatory factor 5 (IRF5) contains polymorphisms associated with these autoimmune diseases. Two of these functional polymorphisms are found upstream of the IRF5 gene. rs2004640, which is a single nucleotide polymorphism and the CGGGG insertion/deletion (indel) were studied. IRF5 uses four different promoters for its four first exons: 1A, 1B, 1C, and 1D. Each promoter was analyzed, including functional differences due to the autoimmune-risk polymorphisms.Results: IRF5 promoters were analyzed using ChIP-Seq data (ENCODE database) and the FactorBook database to define transcription factor binding sites. To verify promoter activity, the promoters were cloned into luciferase plasmids. Each construct exhibited luciferase activity. Exons 1A and 1D contain putative PU.1 and NFkB binding sites. Imiquimod, a Toll-like receptor 7 (TLR7) ligand, was used to activate these transcription factors. IRF5 levels were doubled after imiquimod treatment (p < 0.001), with specific increases in the 1A promoter (2.2-fold, p = 0.03) and 1D promoter (2.8-fold, p = 0.03). A putative binding site for p53, which affects apoptosis, was found in the promoter for exon 1B. However, site-directed mutagenesis of the p53 site showed no effect in a reporter assay.Conclusion: The IRF5 exon 1B promoter has been characterized, and the responses of each IRF5 promoter to TLR7 stimulation have been determined. Changes in promoter activity and gene expression are likely due to specific and distinct transcription factors that bind to each promoter. Since high expression of IRF5 contributes to the development of autoimmune disease, understanding the source of increased IRF5 levels is key to understanding autoimmune etiology.

Epstein-Barr virus-induced gene 2 (EBI2) is an important chemotactic receptor that is involved in proper B-cell T-cell interactions. Epstein-Barr virus (EBV) has been shown to upregulate this gene upon infection of cell lines, but the timing and mechanism of this upregulation, as well as its importance to EBV infection, remain unknown. This work investigated EBV's manipulation of EBI2 expression of primary naive B cells. EBV infection induces EBI2 expression resulting in elevated levels of EBI2 after 24 h until 7 days post-infection, followed by a dramatic decline (P=0.027). Increased EBI2 expression was not found in non-specifically stimulated B cells or when irradiated virus was used. The EBV lytic gene BRRF1 exhibited a similar expression pattern to EBI2 (R2=0.4622). BRRF1-deficient EBV could not induce EBI2. However, B cells transduced with BRRF1 showed elevated expression of EBI2 (P=0.042), a result that was not seen with transduction of a different EBV lytic transfection factor, BRLF1. Based on these results, we conclude that EBI2 expression is directly influenced by EBV infection and that BRRF1 is necessary and sufficient for EBI2 upregulation during infection.