Interferon Regulatory Factor 3 and CREB-Binding Protein/p300 Are Subunits of Double-Stranded RNA-Activated Transcription Factor DRAF1

Abstract

Cells respond to viral infection or double-stranded RNA with the transcriptional induction of a subset of alpha/beta interferon-stimulated genes by a pathway distinct from the interferon signal pathway. The transcriptional induction is mediated through a DNA sequence containing the alpha/beta interferon-stimulated response element (ISRE). We previously identified a novel transcription factor, designated double-stranded RNA-activated factor 1 (DRAF1), that recognizes this response element. The DNA-binding specificity of DRAF1 correlates with transcriptional induction, thereby distinguishing it as a positive regulator of alpha/beta interferon-stimulated genes. Two of the components of DRAF1 have now been identified as interferon regulatory factor 3 (IRF-3) and the transcriptional coactivator CREB-binding protein (CBP)/p300. We demonstrate that IRF-3 preexists in the cytoplasm of uninfected cells and translocates to the nucleus following viral infection. Translocation of IRF-3 is accompanied by an increase in serine and threonine phosphorylation. Coimmunoprecipitation analyses of endogenous proteins demonstrate an association of IRF-3 with the transcriptional coactivators CBP and p300 only subsequent to infection. In addition, antibodies to the IRF-3, CBP, and p300 molecules react with DRAF1 bound to the ISRE target site of induced genes. The cellular response that leads to DRAF1 activation and specific gene expression may serve to increase host survival during viral infection.

IRF-3-dependent and augmented target genes during viral infection

“…[1][2][3][4][5][6][7][8][9][10][11] IRF-3 is expressed constitutively in all cells of the body, and animals with a targeted gene disruption are susceptible to viral infection. 9,10 IRF-3 resides in a latent state primarily in the cytoplasm, but following serine phosphorylation by TANK-binding kinase or inhibitor of NF-kB kinase-related IKKe, it accumulates in the nucleus in strong association with the histone acetyl transferases CREB-binding protein or p300.…”

Single-stranded RNA viruses inactivate the transcriptional activity of p53 but induce NOXA-dependent apoptosis via post-translational modifications of IRF-1, IRF-3 and CREB

“…Recognition of dsRNA by the caspase recruitment domains of the cellular RNA helicases RIG-1 and Mda5, with homology to the caspase recruitment domain proteins (Yoneyama and Fujita, 2004), also leads to phosphorylation of IRF-3. In both cases, phosphorylation of IRF-3 leads to protein homodimerization, translocation to the nucleus and association with co-activator molecules, such as CBP or p300 (Weaver et al, 1998). This complex then binds to the IRF-E element, present within the promoters of type I IFN genes and some ISG genes, resulting in increased transcriptional activity.…”

Contribution of Ser386 and Ser396 to Activation of Interferon Regulatory Factor 3

“…The resultant complex then activates IFN-β transcription. 5,6,7,8,9 Virus-induced phosphoactivation of IRF-3, thought to be mediated directly or indirectly by IKK∈ and/or TBK1, 10,11,12,13,14 occurs in the C-terminal region of IRF-3 at 7 Ser/Thr residues, 385 SSLENTVDLHISNSHPLSLTS 405 4,11,15,16 (Figure 1A). Within this region, IRF-3 has two phosphorylation sites: site 1 includes Ser385 and Ser386, whereas site 2 includes Ser 396, Ser 398, Ser 402, Ser 405, and Thr 404.…”