The gene interferon regulatory factor 5 (IRF5) is a transcription factor which controls immune signaling, cytokine expression, the cell cycle, and apoptosis ( 2– 5). Alternative promoter splicing occurs in around half of human genes ( 1). This is termed alternative promoter splicing, since each first exon must have its own promoter. One type of alternative splicing involves the use of multiple first exons. 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.Īlternative splicing is a method of making different transcripts from one genomic region. Changes in promoter activity and gene expression are likely due to specific and distinct transcription factors that bind to each promoter. However, site-directed mutagenesis of the p53 site showed no effect in a reporter assay.Ĭonclusion: The IRF5 exon 1B promoter has been characterized, and the responses of each IRF5 promoter to TLR7 stimulation have been determined. A putative binding site for p53, which affects apoptosis, was found in the promoter for exon 1B. 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). Imiquimod, a Toll-like receptor 7 (TLR7) ligand, was used to activate these transcription factors. Exons 1A and 1D contain putative PU.1 and NFkB binding sites. Each construct exhibited luciferase activity. To verify promoter activity, the promoters were cloned into luciferase plasmids. Results: IRF5 promoters were analyzed using ChIP-Seq data (ENCODE database) and the FactorBook database to define transcription factor binding sites.

Each promoter was analyzed, including functional differences due to the autoimmune-risk polymorphisms. IRF5 uses four different promoters for its four first exons: 1A, 1B, 1C, and 1D. rs2004640, which is a single nucleotide polymorphism and the CGGGG insertion/deletion (indel) were studied. Two of these functional polymorphisms are found upstream of the IRF5 gene. Interferon regulatory factor 5 (IRF5) contains polymorphisms associated with these autoimmune diseases. Introduction: Autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis affect millions of people worldwide. Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, USA.

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