Thiocyanate supplementation decreases atherosclerotic plaque in mice expressing human myeloperoxidase.

Elevated levels of the heme enzyme myeloperoxidase (MPO) are associated with adverse cardiovascular outcomes. MPO predominantly catalyzes formation of the oxidants hypochlorous acid (HOCl) from Cl(-), and hypothiocyanous acid (HOSCN) from SCN(-), with these anions acting as competitive substrates. HOSCN is a less powerful and more specific oxidant than HOCl, and selectively targets thiols; such damage is largely reversible, unlike much HOCl-induced damage. We hypothesized that increased plasma SCN(-), and hence HOSCN formation instead of HOCl, may decrease artery wall damage. This was examined using high-fat fed atherosclerosis-prone LDLR(-/-) mice transgenic for human MPO, with and without SCN(-) (10 mM) added to drinking water. Serum samples, collected fortnightly, were analyzed for cholesterol, triglycerides, thiols, MPO, and SCN(-); study-long exposure was calculated by area under the curve (AUC). Mean serum SCN(-) concentrations were elevated in the supplemented mice (200-320 µM) relative to controls (< 120 µM). Normalized aortic root plaque areas at sacrifice were 26% lower in the SCN(-)-supplemented mice compared with controls (P = 0.0417), but plaque morphology was not appreciably altered. Serum MPO levels steadily increased in mice on the high-fat diet, however, comparison of SCN(-)-supplemented versus control mice showed no significant changes in MPO protein, cholesterol, or triglyceride levels; thiol levels were decreased in supplemented mice at one time-point. Plaque areas increased with higher cholesterol AUC (r = 0.4742; P = 0.0468), and decreased with increasing SCN(-) AUC (r = - 0.5693; P = 0.0134). These data suggest that increased serum SCN(-) levels, which can be achieved in humans by dietary manipulation, may decrease atherosclerosis burden.

Histamine induces interleukin-6 expression in the human synovial sarcoma cell line (SW982) through the H1 receptor.

METHODS: The effect of histamine on inositol phosphate generation and interleukin-6 (IL-6) release from the synovial sarcoma cell line SW982 was investigated. RESULTS: SW982 cells express functional H1 and H2 receptors. The H1 receptor antagonist [3H]-mepyramine binds to membranes from SW982 cells with high affinity and the binding was potently blocked by H1 antagonists. Histamine potently stimulated phosphoinositide (PI) hydrolysis and Ca2+ mobilization with EC50 of 4.0 +/- 0.8 microM and 1.3 +/- 0.6 microM respectively and these activities were blocked by the H1 selective antagonist mepyramine. Histamine (EC50 = 1.8 +/- 1.1 microM) stimulated the release of IL-6 that was attenuated by selective H1 antagonists. The PKC inhibitor, GF1090203X, blocked the histamine stimulated IL-6 release. The H2 selective antagonist, cimetidine, had no significant effect on histamine-induced PI turnover, Ca2+ mobilization and IL-6 release. CONCLUSION: We conclude that histamine stimulates IL-6 release from SW982 cells by binding to the H1 receptor and this is coupled to the PI/PKC signal transduction pathway. Development of an H1 antagonist that inhibits the release of IL-6 from synoviocytes may be beneficial for the treatment of inflammatory joint disease.

Experimental autoimmune encephalomyelitis develops in CC chemokine receptor 7-deficient mice with altered T-cell responses.

CC chemokine receptor 7 (CCR7) is involved in the initiation of immune responses by mediating the migration of naïve T cells and mature dendritic cells to T-cell-rich zones of secondary lymphoid organs where antigen presentation occurs. To address whether CCR7 plays a role in the development of autoimmunity, we induced experimental autoimmune encephalomyelitis in CCR7-deficient mice on a C57BL/6 background (CCR7(-/-)) using the neuroantigen, myelin oligodendrocyte glycoprotein 35-55 amino acid peptide (MOG((35-55))) and Bordetella pertussis toxin (PTX). CCR7(-/-) mice acquired disease with an intensity similar to wild-type littermates. MOG((35-55))-specific lymphocyte responses were dominant in the spleen of CCR7(-/-) mice, rather than in lymph nodes as observed in wild-type mice. These results indicate that effective immune responses (with altered kinetics) can develop in the absence of CCR7 but develop in the spleen rather than lymph nodes as CCR7 is necessary for T and dendritic cells to enter lymph nodes.

Immunomodulation in type 1 diabetes by NBI-6024, an altered peptide ligand of the insulin B epitope.

NBI-6024 is an altered peptide ligand (APL) corresponding to the 9-23 amino acid region of the insulin B chain (B(9-23)), an epitope recognized by inflammatory interferon-gamma-producing T helper (Th)1 lymphocytes in type 1 diabetic patients. Immunomodulatory effects of NBI-6024 administration in recent-onset diabetic patients in a phase I clinical trial (NBI-6024-0003) were measured in peripheral blood mononuclear cells using the enzyme-linked immunosorbent spot assay. Analysis of the mean magnitude of cytokine responses to B(9-23) and NBI-6024 for each cohort showed significant increases in interleukin-5 responses (a Th2 regulatory phenotype) in cohorts that received APL relative to those receiving placebo. A responder analysis showed that Th1 responses to B(9-23) and NBI-6024 were observed almost exclusively in the placebo-treated diabetic population but not in nondiabetic control subjects and that APL administration (five biweekly subcutaneous injections) significantly and dose-dependently reduced the percentage of patients with these Th1 responses. The results of this phase I clinical study strongly suggest that NBI-6024 treatment shifted the Th1 pathogenic responses in recent-onset type 1 diabetic patients to a protective Th2 regulatory phenotype. The significance of these findings on the clinical outcome of disease is currently under investigation in a phase II multidose study.

Regulation of the PU.1 gene by distal elements.

The transcription factor PU.1 (also known as Spi-1) plays a critical role in the development of the myeloid lineages, and myeloid cells derived from PU.1(-/-) animals are blocked at the earliest stage of myeloid differentiation. Expression of the PU.1 gene is tightly regulated during normal hematopoietic development, and dysregulation of PU.1 expression can lead to erythroleukemia. However, relatively little is known about how the PU.1 gene is regulated in vivo. Here it is shown that myeloid cell type-specific expression of PU.1 in stable cell lines and transgenic animals is conferred by a 91-kilobase (kb) murine genomic DNA fragment that consists of the entire PU.1 gene (20 kb) plus approximately 35 kb of upstream and downstream sequences, respectively. To further map the important transcriptional regulatory elements, deoxyribonuclease I hypersensitive site mapping studies revealed at least 3 clusters in the PU.1 gene. A 3.5-kb fragment containing one of these deoxyribonuclease I hypersensitive sites, located -14 kb 5' of the transcriptional start site, conferred myeloid cell type-specific expression in stably transfected cell lines, suggesting that within this region is an element important for myeloid specific expression of PU.1. Further analysis of this myeloid-specific regulatory element will provide insight into the regulation of this key transcriptional regulator and may be useful as a tool for targeting expression to the myeloid lineage.

Identification and functional analysis of mutations in the hypocretin (orexin) genes of narcoleptic canines.

Narcolepsy is a sleep disorder affecting animals and humans. Exon skipping mutations of the Hypocretin/Orexin-receptor-2 (Hcrtr2) gene were identified as the cause of narcolepsy in Dobermans and Labradors. Preprohypocretin (Hcrt) knockout mice have symptoms similar to human and canine narcolepsy. In this study, 11 sporadic cases of canine narcolepsy and two additional multiplex families were investigated for possible Hcrt and Hcrtr2 mutations. Sporadic cases have been shown to have more variable disease onset, increased disease severity, and undetectable Hypocretin-1 levels in cerebrospinal fluid. The canine Hcrt locus was isolated and characterized for this project. Only one novel mutation was identified in these two loci. This alteration results in a single amino acid substitution (E54K) in the N-terminal region of the Hcrtr2 receptor and autosomal recessive transmission in a Dachshund family. Functional analysis of previously-described exon-skipping mutations and of the E54K substitution were also performed using HEK-293 cell lines transfected with wild-type and mutated constructs. Results indicate a truncated Hcrtr2 protein, an absence of proper membrane localization, and undetectable binding and signal transduction for exon-skipping mutated constructs. In contrast, the E54K abnormality was associated with proper membrane localization, loss of ligand binding, and dramatically diminished calcium mobilization on activation of the receptor. These results are consistent with a loss of function for all three mutations. The absence of mutation in sporadic cases also indicates genetic heterogeneity in canine narcolepsy, as reported previously in humans.

Expression and activity of ADAMTS-5 in synovium.

ADAMTS proteinases, belonging to the adamalysin subfamily of metalloproteinases, have been implicated in a variety of cellular events such as morphogenesis, cell migration, angiogenesis, ovulation and extracellular matrix breakdown. Aggrecanase-1 (ADAMTS-4) and aggrecanase-2 (ADAMTS-5) have been identified in cartilage and are largely responsible for cartilage aggrecan breakdown. We have shown previously that synovium, the membrane lining diarthrodial joints, generates soluble aggrecanase activity. We report here the expression, localization and activity of ADAMTS-5 from human arthritic and bovine synovium. ADAMTS-5 was expressed constitutively in synovium with little or no transcriptional regulation by recombinant human interleukin-1 alpha or all-trans-retinoate, factors previously shown to upregulate aggrecanase activity in cartilage. Aggrecanase activity generated by synovium in vitro and recombinant ADAMTS-5 cleaved aggrecan extensively, resulting in aggrecan fragments similar to those generated by chondrocyte-derived aggrecanases, and the activity was inhibited by heparin. ADAMTS-5 was immunolocalized in human arthritic synovium, where staining was mostly pericellular, particularly in the synovial lining and around blood vessels; some matrix staining was also seen. The possibility that synovium-derived ADAMTS-5 may play a role in cartilage aggrecan breakdown is discussed.

Turning blood into brain: cells bearing neuronal antigens generated in vivo from bone marrow.

Bone marrow stem cells give rise to a variety of hematopoietic lineages and repopulate the blood throughout adult life. We show that, in a strain of mice incapable of developing cells of the myeloid and lymphoid lineages, transplanted adult bone marrow cells migrated into the brain and differentiated into cells that expressed neuron-specific antigens. These findings raise the possibility that bone marrow-derived cells may provide an alternative source of neurons in patients with neurodegenerative diseases or central nervous system injury.

Mesenchymal cells engulf and clear apoptotic footplate cells in macrophageless PU.1 null mouse embryos.

Apoptosis is one of the key tools used by an embryo to regulate cell numbers and sculpt body shape. Although massive numbers of cells die during development, they are so rapidly phagocytosed that very few corpses are ever seen in most embryonic tissues. In this paper, we focus on the catastrophic cell death that occurs as the developing footplate is remodelled to transform webbed regions into free interdigital spaces. In the wild-type embryo, these dead cells are rapidly engulfed and cleared by macrophages. We show that in a macrophageless mouse embryo, null for the haemopoetic-lineage-specific transcription factor, PU.1, the task of phagocytosis is taken over by 'stand-in' mesenchymal neighbours in a clear example of cell redundancy. However, it takes three times as many of these mesenchymal phagocytes to complete the task and, at each stage of the clearance process - in the recognition of apoptotic debris, its engulfment and finally its digestion - they appear to be less efficient than macrophages. A molecular explanation for this may be that several of the engulfment genes expressed by macrophages, including the ABC1 transporter (believed to be part of the phagocytic machinery conserved from Caenorhabditis elegans to mouse), are not upregulated by these 'stand-in' phagocytes.

ADAMTS9, a novel member of the ADAM-TS/ metallospondin gene family.

ADAM-TS/metallospondin genes encode a new family of proteins with structural homology to the ADAM metalloprotease-disintegrin family. However, unlike other ADAMs, these proteins contain thrombospondin type 1 (TSP1) repeats at the carboxy-terminal end and are secreted proteins instead of being membrane bound. Members of the ADAM-TS family have been implicated in the cleavage of proteoglycans, the control of organ shape during development, and the inhibition of angiogenesis. We have cloned a new member of the ADAM-TS/metallospondin family designated here as ADAMTS9. This protein has a metalloprotease domain, a disintegrin-like domain, one internal TSP1 motif, and three carboxy-terminal TSP1-like submotifs. In contrast to other ADAM-TS family members, ADAMTS9 is expressed in all fetal tissues examined as well as some adult tissues. Using FISH and radiation hybrid analysis, we have localized ADAMTS9 to chromosome 3p14.2-p14.3, an area known to be lost in hereditary renal tumors.

Characterization of gamma-aminobutyric acid receptor GABAB(1e), a GABAB(1) splice variant encoding a truncated receptor.

We have identified a splice variant encoding only the extracellular ligand-binding domain of the gamma-aminobutyric acid B (GABA(B)) receptor subunit GABA(B(1a)). This isoform, which we have named GABA(B(1e)), is detected in both rats and humans. While GABA(B(1e)) is a minor component of the total pool of GABA(B(1)) transcripts detected in the central nervous system, it is the primary isoform found in all peripheral tissues examined. When expressed in a heterologous system, the truncated receptor is both secreted and membrane associated. However, GABA(B(1e)) lacks the ability to bind the radiolabeled antagonist [(3)H]CGP 54626A, activate G-protein coupled inwardly rectifying potassium channels, or inhibit forskolin-induced cAMP production when it is expressed alone or together with GABA(B(2)). Interestingly, when co-expressed with GABA(B(2)), not only does the truncated receptor heterodimerize with GABA(B(2)), the association is of sufficient avidity to disrupt the normal GABA(B(1a))/GABA(B(2)) association. Despite this strong interaction, GABA(B(1e)) fails to disrupt G-protein coupled inwardly rectifying potassium activation by the full-length heterodimer pair of GABA(B(1a))/GABA(B(2)).

Transcription factor PU.1 is necessary for development of thymic and myeloid progenitor-derived dendritic cells.

Dendritic cells (DCs) are a heterogeneous population of cells that are specialized for Ag processing and presentation. These cells are believed to derive from both myeloid- and lymphoid-committed precursors. Normal human PBMC-derived, human CD14+ cell (monocyte)-derived, and mouse hematopoietic progenitor-derived DCs were shown to express the hematopoietic cell-restricted, ets family transcription factor PU.1. These populations represent myeloid progenitor-derived DCs. Hematopoietic progenitor cells from PU.1 gene-disrupted (null) mice were unable to generate MHC class IIhigh, CD11c+ myeloid-derived DCs in vitro. Mouse thymic DCs are proposed to be derived from a committed lymphoid progenitor cell that can give rise to T cells as well as DCs. Previously, we showed that CD4 and CD8 T cells developed in PU.1 null mice in a delayed manner and in reduced number. We examined the thymus of 10- to 12-day-old PU.1 null mice and found no evidence of DEC-205+, MIDC-8+ DCs in this tissue. Our findings indicate that PU.1 regulates the development of both thymic and myeloid progenitor-derived populations of DCs, and expand its known role in hematopoietic development.

The copper transport protein Atox1 promotes neuronal survival.

Atox1, a copper transport protein, was recently identified as a copper-dependent suppressor of oxidative damage in yeast lacking superoxide dismutase. We have previously reported that Atox1 in the rat brain is primarily expressed in neurons, with the highest levels in distinct neuronal subtypes that are characterized by their high levels of metal, like copper, iron, and zinc. In this report, we have transfected the Atox1 gene into several neuronal cell lines to increase the endogenous level of Atox1 expression and have demonstrated that, under conditions of serum starvation and oxidative injury, the transfected neurons are significantly protected against this stress. This level of protection is comparable with the level of protection seen with copper/zinc superoxide dismutase and the anti-apoptotic gene bcl-2 that had been similarly transfected. Furthermore, neuronal cell lines transfected with a mutant Atox1 gene, where the copper binding domain has been modified to prevent metal binding, do not afford protection against serum starvation resulting in apoptosis. Therefore, Atox1 is a component of the cellular pathways used for protection against oxidative stress.

Nephroblastoma overexpressed gene (NOV) codes for a growth factor that induces protein tyrosine phosphorylation.

NOV (nephroblastoma overexpressed gene) is a member of the CCN (connective tissue growth factor [CTGF], Cyr61/Cef10, NOV) family of proteins. These proteins are cysteine-rich and are noted for having growth-regulatory functions. We have isolated the rat NOV gene, and the DNA sequence shares 90% identity with the mouse and 80% identity with the human sequences. The rat NOV gene was expressed in all rat tissues examined, including brain, lung, heart, kidney, liver, spleen, thymus and skeletal muscle. Higher levels of rat NOV mRNA were seen in the brain, lung and skeletal muscle compared to the other tissues. Examination of NOV expression in various human cell lines revealed that NOV was expressed in U87, 293, T98G, SK-N-MC and Hs683 but not in HepG2, HL60, THP1 and Jurkat. The human NOV gene was transfected into 293 cells and the expressed protein purified. When 3T3 fibroblasts were treated with this recombinant NOV protein, a dose-dependent increase in proliferation was observed. Analysis of tyrosine-phosphorylated proteins revealed that when 3T3 cells were treated with NOV, a 221 kDa protein was phosphorylated. These data suggest that NOV can act as a growth factor for some cells and binds to a specific receptor that leads to the phosphorylation of a 221 kDa protein.

Mutants of ETS domain PU.1 and GGAA/T recognition: free energies and kinetics.

The ETS family members display specific DNA binding site preferences. As an example, PU.1 and ETS-1 recognize different DNA sequences with a core element centered over 5'-GGAA-3' and 5'-GGAA/T-3', respectively. To understand the molecular basis of this recognition, we carried out site-directed mutagenesis experiments followed by DNA binding studies that use electrophoretic mobility shift assay (EMSA) and surface plasmon resonance methods. EMSA experiments identified amino acid changes A231S and/or N236Y as being important for PU.1 recognition of both 5'-GGAA-3' and 5'-GGAT-3' containing oligonucleotides. To confirm these data and obtain accurate binding parameters, we performed kinetic studies using surface plasmon resonance on these mutants. The N236Y substitution revealed a weak protein-DNA interaction with the 5'-GGAA-3' containing oligonucleotide caused by a faster release of the protein from the DNA (k(off) tenfold higher than the wild-type protein). With the double mutant A231S-N236Y, we obtained an increase in binding affinity and stability toward both 5'-GGAA-3' and 5'-GGAT-3' containing oligonucleotides. We propose that substitution of alanine for serine introduces an oxygen atom that can accept hydrogen and interact with potential water molecules or other atoms to make an energetically favorable hydrogen bond with both 5'-GGAA-3' and 5'-GGAT-3' oligonucleotides. The free energy of dissociation for the double mutant A231S-N236Y with 5'-GGAA-3' (delta deltaG((A231S-N236Y) - (N236Y)) = -1.2 kcal mol confirm the stabilizing effect of this mutant in the protein-DNA complex formation. We conclude that N236Y mutation relaxes the specificity toward 5'-GGAA-3' and 5'-GGAT-3' sequences, while A231S mutation modulates the degree of specificity toward 5'-GGAA-3' and 5'GGAT-3' sequences. This study explains why wild-type PU.1 does not recognize 5'-GGAT-3' sequences and in addition broadens our understanding of 5'-GGAA/T-3' recognition by ETS protein family members.

The transcription factor PU.1 does not regulate lineage commitment but has lineage-specific effects.

PU.1 is a transcription factor shown to regulate the expression of many important genes in myeloid and B cells. At birth, mice homozygous for the disruption of the PU.1 gene have erythrocytes, megakaryocytes, and T cells, but no mature myeloid or B cells. Cells with an inability to develop to maturity were found in this mouse for B cells, neutrophils, eosinophils, mast cells, and monocytes. Rescue of early monocytic cells by transfection with the PU.1 gene results in renewed development to macrophages. These results demonstrate that PU.1 is an important regulator in the development of cells in the hematopoietic system.

PU.1 and the granulocyte- and macrophage colony-stimulating factor receptors play distinct roles in late-stage myeloid cell differentiation.

PU.1 is a hematopoietic cell-specific ets family transcription factor. Gene disruption of PU.1 results in a cell autonomous defect in hematopoietic progenitor cells that manifests as abnormal myeloid and B-lymphoid development. Of the myeloid lineages, no mature macrophages develop, and the neutrophils that develop are aberrantly and incompletely matured. One of the documented abnormalities of PU. 1 null (deficient) hematopoietic cells is a failure to express receptors for granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage (GM)-CSF, and M-CSF. To elucidate the roles of the myeloid growth factor receptors in myeloid cell differentiation, and to distinguish their role from that of PU.1, we have restored expression of the G- and M-CSF receptors in PU.1-deficient cells using retroviral vectors. We have similarly expressed PU.1 in these cells. Whereas expression of growth factor receptors merely allows a PU.1-deficient cell line to survive and grow in the relevant growth factor, expression of PU.1 enables the development of F4/80(+), Mac-1(+)/CD11b(+) macrophages, expression of gp91(phox) and generation of superoxide, and expression of secondary granule genes for neutrophil collagenase and gelatinase. These studies reinforce the idea that availability of PU.1 is crucial for normal myeloid development and clarify some of the molecular events in developing neutrophils and macrophages that are critically dependent on PU.1.

Differentiation of the mononuclear phagocyte system during mouse embryogenesis: the role of transcription factor PU.1.

During mouse embryogenesis, macrophage-like cells arise first in the yolk sac and are produced subsequently in the liver. The onset of liver hematopoiesis is associated with the transition from primitive to definitive erythrocyte production. This report addresses the hypothesis that a similar transition in phenotype occurs in myelopoiesis. We have used whole mount in situ hybridization to detect macrophage-specific genes expressed during mouse development. The mouse c-fms mRNA, encoding the receptor for macrophage colony-stimulating factor (CSF-1), was expressed on phagocytic cells in the yolk sac and throughout the embryo before the onset of liver hematopoiesis. Similar cells were detected using the mannose receptor, the complement receptor (CR3), or the Microphthalmia transcription factor (MITF) as mRNA markers. By contrast, other markers including the F4/80 antigen, the macrophage scavenger receptor, the S-100 proteins, S100A8 and S100A9, and the secretory product lysozyme appeared later in development and appeared restricted to only a subset of c-fms-positive cells. Two-color immunolabeling on disaggregated cells confirmed that CR3 and c-fms proteins are expressed on the same cells. Among the genes appearing later in development was the macrophage-restricted transcription factor, PU.1, which has been shown to be required for normal adult myelopoiesis. Mice with null mutations in PU.1 had normal numbers of c-fms-positive phagocytes at 11.5dpc. PU.1(-/-) embryonic stem cells were able to give rise to macrophage-like cells after cultivation in vitro. The results support previous evidence that yolk sac-derived fetal phagocytes are functionally distinct from those arising in the liver and develop via a different pathway.

Commitment to the monocytic lineage occurs in the absence of the transcription factor PU.1.

Mice homozygous for the disruption of the PU.1 (Spi-1) gene do not produce mature macrophages. In determining the role of PU.1 in macrophage differentiation, the present study investigated whether or not there was commitment to the monocytic lineage in the absence of PU.1. Early PU.1-/- myeloid colonies were generated from neonate liver under conditions that promote primarily macrophage and granulocyte/macrophage colonies. These PU.1-/- colonies were found to contain cells with monocytic characteristics as determined by nonspecific esterase stain and the use of monoclonal antibodies that recognize early monocyte precursors, including Moma-2, ER-MP12, ER-MP20, and ER-MP58. In addition, early myeloid cells could be grown from PU.1-/- fetal liver cultures in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF). Similar to the PU.1 null colonies, the GM-CSF-dependent cells also possessed early monocytic characteristics, including the ability to phagocytize latex beads. The ability of PU.1-/- progenitors to commit to the monocytic lineage was also verified in vivo by flow cytometry and cytochemical analysis of primary neonate liver cells. The combined data shows that PU.1 is absolutely required for macrophage development after commitment to this lineage.

Mutation analysis of the Pip interaction domain reveals critical residues for protein-protein interactions.

The PU.1 interaction partner (Pip) is a member of the interferon regulatory factor family that regulates gene expression through heterodimerization with the ETS transcription factor PU.1. Binding of Pip alone to DNA is weak, and usually it is recruited by phosphorylated PU.1 to form a strong ternary complex with specific DNA sequences. An approach combining sequence homology analysis, secondary structure predictions, and a precise mutational strategy has been used to determine critical residues within the Pip heterodimerization domain that contribute to ternary complex formation. We have delimited the Pip interaction domain to residues 245-422 by using deletion analysis. Site-directed mutagenesis of conserved polar amino acids within two predicted alpha-helices contained in this region, and which are highly conserved in the IRF family, confirmed the importance of these residues for Pip-PU.1 interaction with DNA as well as for trans-activation activity. Our results suggest the existence of a functional epitope essential for heterodimerization between Pip and PU.1 and possibly, in general, between interferon regulatory factor family members and their partners.