Disease relevance of IRF2

• Therefore, we tested association of psoriasis with IRF2 [1].
• Recently it was shown that mice deficient in IRF-2, a transcriptional repressor of IFN signalling and thereby acting as an IRF-1 antagonist, display psoriasis-like skin abnormalities [2].
• Induction of IRF-1 causes growth inhibition in human breast cancer cell lines, and induction of IRF-2 can oppose this [3].
• Alterations in IRF1/IRF2 expression in acute myelogenous leukemia [4].
• However, the major QRE-2-specific binding activity detected within extracts of Burkitt lymphoma cells was attributed to IRF-2, suggesting that interferon-independent activation of Qp is largely mediated by IRF-2 in these cells [5].

High impact information on IRF2

• Following the initial identification of two structurally related members, IRF-1 and IRF-2, seven additional members have now been reported [6].
• In the present study we report the isolation of a cDNA encoding a novel factor, termed IRF-2, that interacts with the same nucleotide sequence elements as IRF-1 [7].
• IRF-2 has been shown to have oncogenic potential, and our results demonstrate a link between IRF-2 and a gene that is functionally coupled to DNA replication and cell-cycle progression at the G1/S phase transition [8].
• When the IRF-2 gene was overexpressed in NIH 3T3 cells, the cells became transformed and displayed enhanced tumorigenicity in nude mice [9].
• Interferon regulatory factor 2 (IRF-2) sites were altered by significantly associated SNPs in two regions [10].

Biological context of IRF2

• Five novel microsatellite markers were developed and typed, and complemented with three known markers to yield a set of eight markers spaced within 600 kb around the IRF2 gene, three of which are located in the gene [1].
• Haplotype sharing analysis confirmed association of IRF2 with type 1 psoriasis (p=0.0017; pcorr=0.03) [1].
• We conclude that a high ratio of IRF1/IRF2 expression may be associated with good cytogenetic and molecular response to IFN-alpha in CML [11].
• Several sets of gel retardation assays with the BPAG1-IRF binding sequence as a probe indicated that IRF1 and IRF2 could bind to the BPAG1-IRF sequence, but some other protein(s), which was induced by IFN-gamma stimulation and possessed binding activity to IRF consensus sequence, showed preferential binding to the BPAG1-IRF sequence [12].
• Computer analysis identified IRF1 and IRF2 consensus sequences between -135 and -123 on BPAG1 promoter region [12].

Anatomical context of IRF2

• Coactivator p300 acetylates the interferon regulatory factor-2 in U937 cells following phorbol ester treatment [13].
• By EMSA, there were marked differences in the induced ratio of IRF-1 and IRF-2 binding activity between the cell lines that correlated with growth inhibition [3].
• Transcriptional regulation of the 230-kDa bullous pemphigoid antigen gene expression by interferon regulatory factor 1 and interferon regulatory factor 2 in normal human epidermal keratinocytes [12].
• Notably, transcription from Qp was not inducible by either alpha or gamma interferon in EBV-negative B cells but rather was shown to be constitutively activated by IRF1 and IRF2 [14].
• Immunoprecipitation of HA-tagged IRF2 expressed in 32P-phosphate labelled COS-7 cells demonstrates that IRF2 is phosphorylated in vivo [15].

Associations of IRF2 with chemical compounds

• Phosphoaminoacid analysis of HA-tagged IRF2 immunoprecipitated from an asynchronous population of proliferating, metabolically phosphate-labelled cells indicates that this protein is phosphorylated exclusively upon serine residues in vivo [15].
• With this probe, the constitutive complex C1/C2 corresponds predominantly to IRF2 [16].
• In C32 cells, an IRF-2 mRNA of 2.4 kb is constitutively expressed in very low amounts but is inducible by Ch-IFN in the absence or presence of cycloheximide [17].

Physical interactions of IRF2

• Interestingly, full-length IRF-2 in TPA-treated U937 cells occurred as a complex with p300 as well as PCAF and was itself acetylated [13].
• Yet, Tyr-phosphorylated ICSBP can bind target DNA only through the association with IRF-2 and IRF-1 [18].
• With B9 cells, there was no IRF-1 binding but instead strong constitutive binding of the IRF-2 repressor, indicating that binding of IRF-1 to DNA is an important regulatory step [19].
• Interaction of IRF-2 and STAT1 on the promoter depends on the DNA-binding domain of IRF-2 [20].
• We show here that IRF-2 physically interacts in vitro with NF-kappa B. This interaction may contribute to the repression of the expression of these genes [21].

Enzymatic interactions of IRF2

• Two-dimensional phosphopeptide mapping of the sites phosphorylated by PKA, PKC, and CKII in vitro demonstrates that these enzymes are capable of phosphorylating IRF2 at multiple distinct sites [15].

Regulatory relationships of IRF2

• IRF1 and its functional antagonist IRF2 originally discovered as transcription factors regulating the interferon-beta (IFN-beta) gene, are involved in the regulation of normal haematopoiesis and leukaemogenesis [22].
• Consistent with alterations in growth characteristics, the IRF-2 DBD transfectants constitutively expressed higher levels of the cyclin dependent kinase inhibitor p21WAF1/Cip1 than did control clones [23].
• In addition, we found that IRF-1 and IRF-2 synergistically activate the CIITA Type IV promoter [24].
• IRF-1 functions as a transcriptional activator, while IRF-2 represses IRF-1 function [25].
• In 293T cells, the transfection of p300/CBP-associated factor (PCAF) enhanced the acetylation of IRF-2 [26].

Other interactions of IRF2

• Using the same cotransfection conditions as for ICSBP, a similar repression of these reporters was observed with IRF-2 [27].
• Consistent with these results, recombinant IRF-2 was acetylated by p300 and to a lesser degree by PCAF in vitro [13].
• We conclude that the bromodomain protein Celtix-1 is a novel IRF-2 interacting protein that associates with transcriptionally active chromatin in situ [28].
• For example, IRF-2 is an activator of the interferon (IFN)-gamma-inducible MHC class II transactivator (CIITA) type IV promoter [29].
• The role of interferon regulatory factor-1 and interferon regulatory factor-2 in IFN-gamma growth inhibition of human breast carcinoma cell lines [3].

Analytical, diagnostic and therapeutic context of IRF2

• Using a panel of IRF-2 deletion mutants in yeast two-hybrid assays, we established that Celtix-1 contacts the C-terminus of IRF-2 [28].
• We confirmed the chromosomal mapping of the human IRF-1 gene to 5q31.1 and newly assigned the IRF-2 gene to 4q35.1, using fluorescence in situ hybridization [30].
• Furthermore, after treatment of promyelocytic HL-60 cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), which triggers differentiation into macrophages, both NMHC-A expression and IRF-2 expression were found to be up-regulated with a similar time course [31].
• RESULTS: Most normal breast tissue showed expression of IRF-1 and no expression of IRF-2 by immunohistochemistry [32].
• Chromatin immunoprecipitation analysis indicated that PCAF transfection increased nucleolin binding to IRF-2 bound to the H4 promoter [26].

References