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Substitution of glycine for arginine at position 127 of the mature human interleukin 1 beta protein generates a mutant IL-1 beta protein (IL-1 beta R----G) which binds cellular IL-1 receptors with high affinity but fails to elicit significant proliferation of T-helper cells (Gehrke, L., Jobling, S. A., Paik, L. S. K., McDonald, B., Rosenwasser, L. J., and Auron, P. E. (1990) J. Biol. Chem. 265, 5922-5925). Although both IL-1 beta and the IL-1 beta R----G mutein stimulate transcription of fibroblast immediate early (fos and jun) and early (IL-1 beta and IL-6) genes, the IL-1 beta R----G mutein, in contrast to the wild-type IL-1 beta protein, induces minimal or no transcription of late genes such as procollagenase and prostromelysin. The effect of the naturally occurring IL-1 receptor antagonist protein (IL-1ra) on fibroblast transcription is distinct from that of the IL-1 beta R----G mutein, for the IL-1ra fails to stimulate not only late (procollagenase and prostromelysin) but also immediate early (fos and jun) gene expression. These data suggest that the IL-I beta R----G mutein triggers an incomplete or defective signal transduction cascade and demonstrate that fibroblast fos and jun expression is not necessarily accompanied by increased transcription of genes containing the AP-1 binding site. These data also suggest that at least two events are required for IL-1-mediated late gene induction in fibroblasts.

We have mapped conserved regions of enhanced DNase I accessibility within the endogenous chromosomal locus of vascular endothelial growth factor A (VEGF-A). Synthetic zinc finger protein (ZFP) transcription factors were designed to target DNA sequences contained within the DNase I-hypersensitive regions. These ZFPs, when fused to either VP16 or p65 transcriptional activation domains, were able to activate expression of the VEGF-A gene as assayed by mRNA accumulation and VEGF-A protein secretion through a range exceeding that induced by hypoxic stress. Importantly, multiple splice variants of VEGF-A mRNA with defined physiological functions were induced by a single engineered ZFP transcription factor. We present evidence for an enhanced activation of VEGF-A gene transcription by ZFP transcription factors fused to VP16 and p65 targeted to two distinct chromosomal sites500 base pairs upstream or downstream of the transcription start site. Our strategy provides a novel approach for dissecting the requirements for gene regulation at a distance without altering the DNA sequence of the endogenous target locus.

Infection of monocytes with human immunodeficiency virus type 1(Ba-L) (HIV-1(Ba-L)) is significantly inhibited by treatment with the serine protease inhibitor, secretory leukocyte protease inhibitor (SLPI). SLPI does not appear to act on virus directly, but rather the inhibitory activity is most likely due to interaction with the host cell. The current study was initiated to investigate how SLPI interacts with monocytes to inhibit infection. SLPI was found to bind to monocytes with high affinity to a single class of receptor sites (approximately 7,000 receptors per monocyte, K(D) = 3.6 nmol/L). The putative SLPI receptor was identified as a surface protein with a molecular weight of 55 +/- 5 kD. A well-characterized function of SLPI is inhibition of neutrophil elastase and cathepsin G. However, two SLPI mutants (or muteins) that contain single amino acid substitutions and exhibit greatly reduced protease inhibitory activity still bound to monocytes and retained anti-HIV-1 activity. SLPI consists of two domains, of which the C-terminal domain contains the protease inhibiting region. However, when tested independently, neither domain had potent anti-HIV-1 activity. SLPI binding neither prevented virus binding to monocytes nor attenuated the infectivity of any virus progeny that escaped inhibition by SLPI. A polymerase chain reaction (PCR)-based assay for newly generated viral DNA demonstrated that SLPI blocks at or before viral DNA synthesis. Therefore, it most likely inhibits a step of viral infection that occurs after virus binding but before reverse transcription. Taken together, the unique antiviral activity of SLPI, which may be independent of its previously characterized antiprotease activity, appears to reside in disruption of the viral infection process soon after virus binding.

Interleukin-1 receptor antagonist (IL-1ra), an IL-1 family member, binds with high affinity to the type I IL-1 receptor (IL-1RI), blocking IL-1 binding but not inducing an IL-1-like response. Extensive site-directed mutagenesis has been used to identify residues in IL-1ra and IL-1 beta involved in binding to IL-1RI. These analyses have revealed the presence of two discrete receptor binding sites on IL-1 beta. Only one of these sites is present on IL-1ra, consisting of residues Trp-16, Gln-20, Tyr-34, Gln-36, and Tyr-147. Interestingly, the absent second site is at the location of the major structural difference between IL-1ra and IL-1 beta, which are otherwise structurally similar. The two receptor binding sites on IL-1 beta are also present on IL-1 alpha. Thus, it appears that the two IL-1 agonist molecules have two sites for IL-1RI binding, and the homologous antagonist molecule, IL-1ra, has only one. Based on these observations, a hypothesis is presented to account for the difference in activity between the agonist and antagonist proteins. It is proposed that the presence of the two receptor binding sites may be necessary for agonist activity.

Genomic and cDNA clones for rabbit interleukin-1 receptor antagonist (IL-1ra) were isolate based on homology with the human, mouse, and rat IL-1ra gene. A partial genomic clone, obtained by screening a rabbit genomic library, contained coding sequences for the carboxyl-terminal 108 amino acids of rabbit IL-1ra. Two classes of cDNA for rabbit IL-1ra were obtained using RNA from inflamed rabbit colon tissue. One class of cDNA coded for a secreted form of IL-1ra, whereas the other coded for a putative intracellular form of rabbit IL-1ra. The latter form is similar to that isolated from human epithelial cells. A partially synthetic rabbit IL-1ra gene was constructed and expressed in Escherichia coli. The recombinant rabbit IL-1ra was purified to homogeneity by ion exchange chromatography. Its affinity was similar to that of human IL-1ra for the human and mouse type I IL-1 receptor. From the cDNA clone and the purified recombinant protein, specific probes were developed for measuring levels of rabbit IL-1ra mRNA and protein in normal and inflamed rabbit tissues. Unlike IL-1 alpha and IL-1 beta, IL-1RA mRNA and protein were present at detectable levels in normal rabbit colon. During the development of an experimental formalin-immune complex colitis, rabbit IL-1 alpha showed a dramatic increase in tissue levels, consistent with previous results; IL-1ra also increased 3-4-fold. Treatment of colitis rabbits with corticosteroids significantly suppressed neutrophil infiltration, corticosteroid treatment suppressed IL-1ra but not IL-1 alpha mRNA steady-state levels. Our observations demonstrate that IL-1 and IL-1ra synthesis is differentially regulated in healthy and inflamed intestinal tissue.

Sustained release or high levels of interleukin-1 (IL-1) and/or tumor necrosis factor (TNF), as observed after endotoxin challenge, can produce a variety of toxicities. Naturally occurring inhibitors to IL-1 and TNF, IL-1 receptor antagonist (IL-1ra) and soluble TNF receptor forms, have been detected. These proteins may function to buffer or limit the effects of these cytokines as part of a regulatory network. As part of a clinical trial of recombinant human interleukin-1 beta (rhIL-1 beta), serial plasma samples were obtained from 6 patients with metastatic melanoma treated with 30-min infusions of rhIL-1 beta for 5 consecutive days. The presence of circulating IL-1 receptor antagonist and soluble TNF binding proteins (TNF-R55-BP and TNF-R75-BP) were assessed. A maximum 86-fold increase for IL-1ra, a 7-8-fold increase for TNF-R55-BP, and a 2-3-fold increase for TNF-R75-BP were seen 2-4 h, 1 h, and 4 h, respectively, after rhIL-1 beta infusion. On each day of the treatment, the secretion of IL-1ra and release of TNF-R55-BP was observed, but there was no accumulation above baseline value for IL-1ra before each of the 5 daily infusions. Although there was a steady decrease of the 6-h postinfusion plasma levels for IL-1ra and TNF-R55-BP over the 5 treatment days, no increase of clinical side effects was noted. Two patients had measurable levels of TNF-alpha, but no correlation to TNF-binding proteins was observed. Our data show that early after rhIL-1 beta infusion the induction of IL-1ra secretion, as well as TNF-binding protein release, is observed.

We have examined the binding of human and rodent interleukin-1 receptor antagonist (IL-1ra) to the type II IL-1 receptor on the human B cell line, Raji, on the mouse pre-B cell line, 70Z/3, and on human polymorphonuclear leukocytes (PMNs). Human IL-1ra binds to the receptors on the human B cells with an affinity (KD = 15 +/- 3 nM) equal to that of IL-1 alpha and only 15-fold lower than that of IL-1 beta and, likewise, binds to human PMNs with an affinity (KD = 8 +/- 4 nM) 15-fold lower than that of IL-1 beta. Mouse and rat IL-1ra bind to these two human cell types with an affinity similar to that of the human protein. Human IL-1ra binds very weakly to the type II receptor on the mouse pre-B cells with an affinity (KD = 1.4 +/- 0.2 microM) about 1500-fold lower than human IL-1 beta. Mouse and rat IL-1ra also bind to the mouse pre-B cells with low affinity. The weak binding of the three IL-1ra proteins to these mouse cells appears to be more a consequence of the cell type rather than species specificity. There may be a population of cells for which the actions of IL-1 cannot be effectively opposed by IL-1ra, although this group does not include mature B cells and PMNs.

Substitution of glycine for arginine at position 127 of the mature human interleukin 1 beta protein generates a mutant IL-1 beta protein (IL-1 beta R----G) which binds cellular IL-1 receptors with high affinity but fails to elicit significant proliferation of T-helper cells (Gehrke, L., Jobling, S. A., Paik, L. S. K., McDonald, B., Rosenwasser, L. J., and Auron, P. E. (1990) J. Biol. Chem. 265, 5922-5925). Although both IL-1 beta and the IL-1 beta R----G mutein stimulate transcription of fibroblast immediate early (fos and jun) and early (IL-1 beta and IL-6) genes, the IL-1 beta R----G mutein, in contrast to the wild-type IL-1 beta protein, induces minimal or no transcription of late genes such as procollagenase and prostromelysin. The effect of the naturally occurring IL-1 receptor antagonist protein (IL-1ra) on fibroblast transcription is distinct from that of the IL-1 beta R----G mutein, for the IL-1ra fails to stimulate not only late (procollagenase and prostromelysin) but also immediate early (fos and jun) gene expression. These data suggest that the IL-I beta R----G mutein triggers an incomplete or defective signal transduction cascade and demonstrate that fibroblast fos and jun expression is not necessarily accompanied by increased transcription of genes containing the AP-1 binding site. These data also suggest that at least two events are required for IL-1-mediated late gene induction in fibroblasts.

The interleukin-1 receptor antagonist (IL-1ra) is a protein capable of inhibiting receptor binding and biological activities of IL-1 without inducing an IL-1-like response. Equilibrium binding and kinetic experiments show that IL-1ra binds to the 80-kDa IL-1 receptor on the murine thymoma cell line EL4 with an affinity (KD = 150 pM) approximately equal to that of IL-1 alpha and IL-1 beta for this receptor. However, IL-1ra is unable to induce two early events associated with IL-1 activity. Surface-bound IL-1ra does not undergo receptor-mediated internalization, and IL-1ra does not activate the protein kinase activity responsible for down-modulation of the EGF receptor on the murine 3T3 fibroblast cell line. The failure to induce general, early responses characteristic of IL-1 indicates that IL-1ra is unlikely to act as an agonist on any cell expressing the 80-kDa receptor.

Interleukin 1 (IL-1) receptor antagonist (IL-1ra) is a naturally occurring protein that binds to the IL-1 receptor present on T cells, fibroblasts, and other cell types and acts to block IL-1-induced responses. IL-1ra is a pure antagonist and has no agonist activity in in vitro or in vivo systems. By site-specific mutagenesis, an analog of IL-1ra was created that contained a substitution of a single amino acid, Lys-145----Asp. This analog, IL-1ra K145D, exhibited partial agonist activity in the D10.G4.1 cell proliferation assay. The newly acquired agonist activity could not be neutralized by antisera to IL-1 alpha or IL-1 beta, but it could be blocked by a monoclonal antibody to the T-cell IL-1 receptor. The analog also showed agonist activity as assayed by increased prostaglandin E2 synthesis from CHO cells expressing recombinant mouse IL-1 receptor. These results with IL-1ra K145D demonstrate the importance of the region surrounding the corresponding Asp-145 residue in IL-1 beta for triggering the biological response to IL-1.

Endotoxin, a lipopolysaccharide (LPS) component of gram-negative bacteria, induces alveolar macrophages to express interleukin-1 (IL-1). Lipopolysaccharide and IL-1 both cause severe acute neutrophilic inflammation in the lung after intratracheal injection, suggesting that LPS-induced IL-1 expression contributes to the pathogenesis of LPS-induced acute inflammation. In the present study, the role of IL-1 in LPS-induced acute pneumonia was investigated by quantitating the acute inflammation occurring at 6 hours after the intratracheal injection of LPS as compared to the same timepoint after the intratracheal coinjection of LPS and IL-1 receptor antagonist (IL-1ra). The IL-1ra was found to inhibit LPS-induced acute inflammation (P greater than 0.0001) as measured by the number of neutrophils recovered in bronchoalveolar lavage. The LPS-induced emigration of neutrophils was inhibited by as much as 45%. Recombinant IL-1 beta-induced neutrophil emigration into the lung was inhibited by 95% when IL-1ra was coinjected intratracheally with IL-1 beta. Coinjection of recombinant IL-1 beta and LPS increased the neutrophilic exodus as compared to the intratracheal injection of either agent alone. Intratracheal injection of LPS induces a progressive increase in IL-1ra mRNA expression in whole-lung RNA preparations, suggesting that endogenous IL-1ra may play an important role as a negative feedback mechanism to downregulate LPS initiated IL-1-mediated acute inflammation. In conclusion IL-1ra inhibits both LPS- and IL-1-induced neutrophilic inflammation and may therefore prove clinically useful as an anti-inflammatory agent for the therapy of either septic or aseptic IL-1-mediated acute inflammation.

A transient expression assay was used to measure the relative template activities of mutated tk genes in mouse L cells induced in trans by herpes simplex virus (HSV). In this assay, expression of the wild-type HSV type 1 tk gene is induced at least 200-fold by the superinfecting virus. Genetic lesions that were assayed include 5' deletions, clustered base substitutions, single base substitutions, intrapromoter inversions, and intrapromoter recombinants with the HSV type 2 tk gene. Roughly half of the mutations that were tested were found to weaken tk expression efficiency, and the remaining mutations did not alter expression. The spatial distribution of mutations that reduce expression efficiency in trans-induced mouse fibroblasts facilitated the construction of a map of promoter domains. The most gene-proximal promoter domain is located between 16 and 32 base pairs (bp) upstream of the tk mRNA cap site and contains a TATA homology. Two more distally located promoter domains were mapped to discrete locations upstream from the TATA homology. One of these distal domains is located between 47 and 79 bp upstream from the mRNA cap site, and the other is located between 84 and 105 bp upstream from the tk gene. The boundaries of these three promoter domains, with one exception, coincided with the set of domains delineated previously in a frog oocyte microinjection assay. The concordant behavior of tk promoter mutants in microinjected frog oocytes and trans-induced mouse fibroblasts leads us to propose that recognition and activation of the HSV tk promoter is mediated by cellular transcription factors that are common to frogs and mice.

The Moloney murine sarcoma virus long terminal repeat (LTR) harbors two distinct positive activators of transcription, namely, a distal signal and an enhancer. In this report we demonstrate that infection by herpes simplex virus (HSV) can markedly affect the utilization of these two Moloney murine sarcoma virus transcription signals. We investigated the HSV-mediated trans-acting effects with two goals in mind: first, to gain insight into LTR function, and second, to probe the mechanisms used by HSV to establish its own transcription cascade. In mock-infected cells, LTR-mediated expression was heavily dependent on the Moloney murine sarcoma virus enhancer but was effectively distal signal independent. HSV infection mobilized the use of the LTR distal signal and concomitantly alleviated enhancer dependence. Indeed, enhancer function may actually be inhibited by HSV trans-acting factors. These results suggest that the two positive control signals of the Moloney murine sarcoma virus LTR facilitate transcriptional activation by two different pathways. We further observed that the identity of the structural gene driven by the LRT, as well as the state of integration of a transfected template, can exert a substantial effect on the response of a template to HSV infection. According to these findings, we propose a tentative model to account for the initial temporal shift of the HSV transcriptional cascade.

The expression of the positively charged human protein secretory leukocyte protease inhibitor (SLPI) in Escherichia coli causes severe cellular toxicity. After induction of SLPI synthesis in a high-level-expression strain, SGE61, the growth of the strain is arrested and total protein and RNA synthesis rates decline by 60 to 70%. The mechanism of SLPI-mediated inhibition of macromolecular synthesis was examined in cell-free transcription-translation systems. SLPI proved to be a potent inhibitor of translation in vitro. When SLPI was added to translation reactions at SLPI/mRNA ratios attained during maximal SLPI accumulation in SGE61, translation of a test mRNA was inhibited by 75%. The mechanism of translation inhibition was deduced from in vitro experiments showing that SLPI bound to mRNA and interfered with the interaction of RNA-metabolizing enzymes, such as RNase. In addition, SLPI bound to DNA in vitro, but transcription was not inhibited as strongly in cell-free reactions as it was in SGE61. Similar nucleic acid-binding and translation inhibition properties were displayed in vitro by another basic protein, chicken egg white lysozyme, but were not displayed by the relatively acidic protein bovine serum albumin. On the basis of these results, we concluded that SLPI binds to nucleic acids via charge interactions and inhibits translation by competing with ribosomes for binding to mRNA. Since SLPI-mRNA and SLPI-DNA binding occurred at SLPI/mRNA and SLPI/DNA ratios existing in SGE61, nucleic acid binding may contribute to the toxicity of SLPI to E. coli. These results indicate that, in general, high-level expression of basic recombinant proteins in E. coli may be problematic.

The cDNA sequence coding for human basic fibroblast growth factor (bFGF) has been cloned downstream of a transcription promoter recognized by the bacteriophage T7 RNA polymerase. Initiation of translation at the fgf gene has been coupled to upstream translation of a fragment of the T7 phi 10 gene. Expression of the fgf gene in this system can lead to an accumulation of approximately 40 mg/liter/A600 unit of bFGF. This material can be purified close to homogeneity from a soluble protein extract on a heparin-Sepharose column. bFGF so obtained has been shown to have bioactivity indistinguishable from human placental fibroblast growth factor in mitogenicity, synthesis of plasminogen activator, and angiogenesis assays.

A temperature-sensitive (t.s.) tRNATrp from Escherichia coli has a single base change from the wild type (w.t.) species, which results in the loss of a base pair at the bottom of the CCA stem of the cloverleaf structure. Thermodynamic studies on this t.s. tRNA show that it is more susceptible to denaturation than the w.t. due to a larger change in the entropy of denaturation. Correlated with this thermodynamic result is the finding that the denatured t.s. tRNA's T psi C loop is more susceptible to digestion by T1 RNase, suggesting that it has greater freedom than the corresponding structure on the denatured w.t. molecule. In contrast, the native form of the t.s. tRNATrp is very similar to the w.t. with regard to aminoacylation, T1 RNase susceptibility, and column chromatographic mobility, despite the fact that it necessarily has one less base pair. In addition, the well known denaturation-dependent shift in column chromatographic mobility, which is observed for both the t.s. and w.t. molecules, depends on a modification in the anticodon loop, since tRNATrp lacking that modification does not shift when denatured. Thus, though it is not usually thought to be implicated, denaturation probably affects the conformation of the anticodon loop. The lethal phenotype of the mutant at high temperature, defective attenuation of the tryptophan biosynthetic operon in the mutant, and some aspects of the denatured state are clarified by these findings.