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1.  Differential Requirement of Histone Acetylase and Deacetylase Activities for IRF5-Mediated Proinflammatory Cytokine Expression 
Recent evidence indicates a new role for histone deacetylases (HDACs) in the activation of genes governing the host immune response. Virus, along with other pathogenic stimuli, triggers an antiviral defense mechanism through the induction of IFN, IFN-stimulated genes, and other proinflammatory cytokines. Many of these genes have been shown to be regulated by transcription factors of the IFN regulatory factor (IRF) family. Recent studies from IRF5 knockout mice have confirmed a critical role for IRF5 in virus-induced type I IFN expression and proinflammatory cytokines IL-6, IL-12, and TNF-α; yet, little is known of the molecular mechanism of IRF5-mediated proinflammatory cytokine expression. In this study, we show that both HDACs and histone acetyltransferases (HATs) associate with IRF5, leading to alterations in its transactivation ability. Using the HDAC inhibitor trichostatin A, we demonstrate that ISRE, IFNA, and IL6 promoters require HDAC activity for transactivation and transcription, whereas TNFα does not. Mapping the interaction of corepressor proteins (HDAC1, silencing mediator of retinoid and thyroid receptor/nuclear corepressor of retinoid receptor, and Sin3a) and HATs to IRF5 revealed distinct differences, including the dependence of IRF5 phosphorylation on HAT association resulting in IRF5 acetylation. Data presented in this study support a mechanism whereby virus triggers the dynamic conversion of an IRF5-mediated silencing complex to that of an activating complex on promoters of target genes. These data provide the first evidence, to our knowledge, of a tightly controlled transcriptional mechanism whereby IRF5 regulates proinflammatory cytokine expression in conjunction with HATs and HDACs.
PMCID: PMC3233222  PMID: 20935208
2.  Genetic variants and disease-associated factors contribute to enhanced IRF-5 expression in blood cells of systemic lupus erythematosus patients 
Arthritis and rheumatism  2010;62(2):562-573.
Genetic variants of the interferon (IFN) regulatory factor 5 (IRF5) gene are associated with systemic lupus erythematosus (SLE) susceptibility. The contribution of these variants to IRF-5 expression in primary blood cells of SLE patients has not been addressed, nor has the role of type I IFN. The aim of this study was to determine the association between increased IRF-5 expression and the IRF5 risk haplotype in SLE patients.
IRF-5 transcript and protein levels in 44 Swedish patients with SLE and 16 healthy controls were measured by quantitative real-time PCR, minigene assay, and flow cytometry. The rs2004640, rs10954213, rs10488631 and the CGGGG indel were genotyped in these patients. Genotypes of these polymorphisms defined a common risk and protective haplotype.
IRF-5 expression and alternative splicing were significantly upregulated in SLE patients versus healthy donors. Enhanced transcript and protein levels were associated with the risk haplotype of IRF5; rs10488631 gave the only significant independent association that correlated with increased transcription from non-coding exon 1C. Minigene experiments demonstrated an important role for rs2004640 and the CGGGG indel, along with type I IFNs in regulating IRF-5 expression.
This study provides the first formal proof that IRF-5 expression and alternative splicing are significantly upregulated in primary blood cells of SLE patients. The risk haplotype is associated with enhanced IRF-5 transcript and protein expression in SLE patients.
PMCID: PMC3213692  PMID: 20112383
3.  Histone deacetylase inhibitors: A new mode for inhibition of cholesterol metabolism 
BMC Genomics  2008;9:507.
Eukaryotic gene expression is a complex process involving multiple cis and trans activating molecules to either facilitate or inhibit transcription. In recent years, many studies have focused on the role of acetylation of histone proteins in modulating transcription, whereas deacetylation of these same proteins is associated with inactivation or repression of gene expression. This study explores gene expression in HepG2 and F9 cell lines treated with Trichostatin A (TSA), a potent histone deacetylase inhibitor.
These experiments show that TSA treatment results in clear repression of genes involved in the cholesterol biosynthetic pathway as well as other associated pathways including fatty acid biosynthesis and glycolysis. TSA down regulates 9 of 15 genes in this pathway in the F9 embryonal carcinoma model and 11 of 15 pathway genes in the HepG2 cell line. A time course study on the effect of TSA on gene expression of various enzymes and transcription factors involved in these pathways suggests that down regulation of Srebf2 may be the triggering factor for down regulation of the cholesterol biosynthesis pathway.
Our results provide new insights in the effects of histone deacetylases on genes involved in primary metabolism. This observation suggests that TSA, and other related histone deacetylase inhibitors, may be useful as potential therapeutic entities for the control of cholesterol levels in humans.
PMCID: PMC2613157  PMID: 18959802

Results 1-3 (3)