A novel 7-nucleotide motif located in 3' untranslated sequences of the immediate-early gene set mediates platelet-derived growth factor induction of the JE gene

MCP-1: chemoattractant with a role beyond immunity: a review

BACKGROUND

Monocyte Chemoattractant Protein (MCP)-1, a potent monocyte attractant, is a member of the CC chemokine subfamily. MCP-1 exerts its effects through binding to G-protein-coupled receptors on the surface of leukocytes targeted for activation and migration. Role of MCP-1 and its receptor CCR2 in monocyte recruitment during infection or under other inflammatory conditions is well known.

METHOD

A comprehensive literature search was conducted from the websites of the National Library of Medicine (http://www.ncbl.nlm.nih.gov) and Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/). The data was assessed from books and journals that published relevant articles in this field.

RESULT

Recent and ongoing research indicates the role of MCP-1 in various allergic conditions, immunodeficiency diseases, bone remodelling, and permeability of blood - brain barrier, atherosclerosis, nephropathies and tumors.

CONCLUSION

MCP-1 plays an important role in pathogenesis of various disease states and hence MCP-1 inhibition may have beneficial effects in such conditions.

EGF- and cell-cycle-regulated STAG1/PMEPA1/ERG1.2 belongs to a conserved gene family and is overexpressed and amplified in breast and ovarian cancer

The abnormal activation of the epidermal growth factor (EGF) pathway is one of the most common findings in human cancer, and a number of molecular devices of laboratory and clinical relevance have been designed to block this transduction pathway. Because of the large number of cellular events that might be regulated through the activation of the four EGF receptor family members, it is possible that screening methodologies for the identification of new molecular targets working downstream of these pathways may provide new tools for cancer diagnosis and potentially prevention and therapy. In searching for EGF target genes, we have identified ERG1.2, the mouse homolog of the solid tumor-associated gene STAG1. Both in humans and in mice, it belongs to a new gene family that can give origin to several protein isoforms through alternative splicing and/or multiple translation starts. Sequence analysis and experimental data suggest that ERG1.2 is likely to function as a membrane-bound protein interacting with downstream signaling molecules through WW- and SH3-binding domains. ERG1.2 is a cell-cycle-regulated gene, and both ERG1.2 and STAG1 are induced by EGF and other growth factors at the transcript and protein levels. Finally, we have demonstrated that, besides prostate cancer and renal cell carcinoma, STAG1 was also overexpressed in breast and ovarian cancer cell lines and in breast primary tumors. Although in most cases STAG1 overexpression is probably due to the abnormal activation of the EGF pathway, we have also demonstrated genetic amplification and rearrangement of its locus in one breast cancer cell line and one primary ovarian cancer, suggesting that STAG1 might be a direct molecular target in the carcinogenetic process. Thus its overexpression might be regarded not only as a tumor marker but also as a potentially pathogenetic event.

AP1 genes in Fugu indicate a divergent transcriptional control to that of mammals

The draft genomic sequence of the Japanese puffer fish, Fugu rubripes, has now been announced. This is the first complete sequence of a teleost fish and the second available vertebrate sequence, the first being that of human. For the first time, whole-genome comparisons between two vertebrates can be undertaken. Early analysis has suggested that there may be surprising differences in gene regulation between human and fish. In mammals, a gene commonly has several functions, and this may not always be the case in fish. Many gene families comprise more members in fish than they do in mammals, possibly because each fish gene has evolved an individual function. Complexities of gene regulation in mammals has hampered studies of all biological processes from cell proliferation to cell death. Determining the activities of the AP1 transcription factor proteins has been non-trivial. The AP1 complex typically comprises two proteins, a Jun (c-Jun, JunB, and JunD) and a Fos (c-Fos, FosB, Fra1, and Fra2). These proteins can form both homodimers and heterodimers among-themselves and can interact with additional proteins; thus, dissecting their individual roles has been difficult. We have determined that Fugu has more Jun and Fos genes than mammals, and if each proves to have a separate function, then addressing the roles of the individual AP1 proteins in Fugu may be simpler than in human.

Alivin 1, a novel neuronal activity-dependent gene, inhibits apoptosis and promotes survival of cerebellar granule neurons

Neurons require Ca2+-dependent gene transcription for their activity-dependent survival, the mechanisms of which have not been fully elucidated yet. Here, we demonstrate that a novel primary response gene, alivin 1 (ali1), is an activity-dependent gene and promotes survival of neurons. Sequence analyses reveal that rat, mouse, and human Ali1 proteins contain seven leucine-rich repeats, one IgC2-like loop and a transmembrane domain, and display homology to Kek and Trk families. Expression of ali1 mRNA in cultured cerebellar granule neurons is rigidly regulated by KCl and/or NMDA concentrations in the culture medium and tightly correlated to depolarization-dependent survival and/or NMDA-dependent survival of the granule neuron. ali1 mRNA expression was regulated at the transcriptional step by the Ca2+ influx through voltage-dependent L-type Ca2+ channels when the cells were stimulated by 25 mm KCl. Expression of ali1 mRNA in cultured cortical neurons was inhibited when their spontaneous electrical activity was blocked by tetrodotoxin. Thus, the expression is neuronal activity dependent. Overexpression of Ali1 in cerebellar granule neurons inhibited apoptosis that was induced by the medium containing 5 mm KCl. The addition of anti-Ali1 antiserum or the soluble putative extracellular Ali1 domain to the 25 mm KCl-supported culture inhibited the survival of the granule neuron. These results suggest that expression of ali1 promotes depolarization-dependent survival of the granule neuron. Mouse ali1 was mapped to a locus approximately 55.3 cM from the centromere on chromosome 15 that is syntenic to positional candidate loci for familial Alzheimer's disease type 5 and Parkinson's disease 8 on human chromosome 12.

Chick RGS2L demonstrates concentration-dependent selectivity for pertussis toxin-sensitive and -insensitive pathways that inhibit L-type Ca2+ channels

In neuronal cells, the influx of Ca2+ ions through voltage-dependent L-type calcium (L) channels couples excitation to multiple cellular functions. In addition to voltage, several neurotransmitters, hormones and cytokines regulate L channel gating via binding to G-protein-coupled receptors. Intracellular molecules that modify G-protein activity - such as regulator of G-protein-signalling (RGS) proteins - are therefore potential candidates for regulating Ca2+ influx through L channels. Here we show that a novel RGS2 splice variant from chick dorsal root ganglion (DRG) neurons, RGS2L, reduces bradykinin (BK)-mediated inhibition of neuronal L channels and accelerates recovery from inhibition. Chick RGS2 reduces the inhibition mediated by both the pertussis toxin (PTX)-sensitive (Gi/o-coupled) and the PTX-insensitive (presumably Gq/11-coupled) pathways. However, we demonstrate for the first time in a living cell that the extent of coupling to each pathway varies with RGS2L concentration. A low concentration of recombinant chick RGS2L (10 nM) preferentially reduces the inhibition mediated by the PTX-insensitive pathway, whereas a 100-fold higher concentration attenuates both PTX-sensitive- and PTX-insensitive-mediated components equally. Our data suggest that factors promoting RGS2L gene induction may regulate Ca2+ influx through L channels by recruiting low-affinity interactions with Gi/o that are absent at basal RGS2L levels.

Unique isoform of Galpha -interacting protein (RGS-GAIP) selectively discriminates between two Go-mediated pathways that inhibit Ca2+ channels

Regulators of G-protein signaling (RGS) proteins constitute a large family of GTPase-activating proteins for heterotrimeric G proteins. More than 20 RGS genes have been identified in mammals. One of these, the Galpha-interacting protein (GAIP), preferentially interacts with members of the G(i)/G(o) subfamily of G proteins in mammalian cells, but its selectivity among members of this subfamily in vitro is limited. Here we report the cloning and functional characterization of a unique cDNA isoform of GAIP, derived from embryonic chicken dorsal root ganglion neurons. Chick GAIP is composed of 199 amino acids, organized into a conserved RGS domain (85% identical to human GAIP), and a unique, short N terminus (only 41% identical, 50% homologous to known mammalian orthologues). Consistent with this unique primary structure, chick GAIP has physiological properties that distinguish it from mammalian GAIPs. We have explored the selectivity of chick GAIP in electrophysiological assays of two G(o)-mediated forms of Ca(2+) channel inhibition produced by gamma-aminobutyric acid in chick dorsal root ganglion neurons, voltage-independent inhibition (mediated by G(o)alpha) and voltage-dependent inhibition (mediated by G(o)betagamma). Dialyzing recombinant chick GAIP in these cells selectively reduced voltage-independent inhibition without affecting voltage-dependent inhibition. Mammalian GAIP, tested under identical conditions in previous studies, demonstrated no selectivity between these two inhibitory processes; thus, our results suggest that the functional specificity of chick GAIP is likely to be determined by its unique N terminus.

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit chemokine production in activated microglia

Microglia react to even minor disturbances in CNS homeostasis and function as critical regulators of CNS inflammation. Activated microglia secrete inflammatory mediators such as cytokines and chemokines, which contribute to the pathophysiological changes associated with several neuroimmunologic disorders. Microglia-derived inflammatory chemokines recruit various populations of immune cells, which initiate and maintain the inflammatory response against foreign antigens. Entry and retention of activated immune cells in the CNS is a common denominator in a variety of traumatic, ischemic, and degenerative diseases. Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are two structurally related neuropeptides that function as potent anti-inflammatory factors in the periphery. Here we investigated the effects of VIP and PACAP on chemokine production by activated microglia. VIP and PACAP inhibit the expression of the microglia-derived CXC chemokines MIP-2 and KC, and of the CC chemokines MIP-1alpha, -1beta, MCP-1, and RANTES. The inhibition of chemokine gene expression correlates with an inhibitory effect of VIP/PACAP on NFkB binding. The VIP/PACAP inhibition of both chemokine production and of NFkB binding is mediated through the specific receptor VPAC1 and involves a cAMP-dependent intracellular pathway. Of biological significance is the fact that the inhibition of chemokine production by VIP/PACAP leads to a significant reduction in the chemotactic activity generated by activated microglia for peripheral leukocytes, i.e., neutrophils, macrophages, and lymphocytes. Because reduction in the number and activation of infiltrating leukocytes represents an important factor in the control of inflammation in the CNS, VIP and/or PACAP released by neurons during an inflammatory response could serve as neuronal survival factors by limiting the inflammatory process.

Identification of new regulatory sequences far upstream of the mouse monocyte chemoattractant protein-1 gene

We systematically searched for sequences influencing the expression of the mouse monocyte chemoattractant protein-1 (MCP-1) gene (Scya2) by mapping DNase I hypersensitive sites (HS) in the chromatin of mesangial cells in a 40-kb interval around the gene. We found nine HS located between -24 kb and +12.7 kb. Three HS coincided with previously known regulatory sequences (HS-2.4, HS-1.0, and HS-0.2). We tested two of the previously unknown HS located far upstream of Scya2 (HS-19.4 and HS-16.3) in transfection experiments using luciferase reporter constructs and mouse mesangial cells as recipients. In transient transfections, both HS had a moderate effect on basal promoter activity as well as promoter activity stimulated by tumor necrosis factor-alpha. In stable transfection experiments, we found much higher activity. A DNA fragment containing HS-19.4 and HS-16.3 caused a considerable increase in the number of stably integrated luciferase copies. We determined the nucleotide sequence of the 5' flanking region to -28.6 kb. Computer-assisted sequence analysis did not yield evidence of an additional gene. These HS are located within the 5' flanking region of a gene cluster consisting of Scya2 (MCP-1), Scya7 (MCP-3), Scya11 (eotaxin), Scya12 (MCP-5), and Scya8 (MCP-2). This report represents the first comprehensive chromatin analysis of the mouse MCP-1 locus leading to the identification of a complex regulatory region located far upstream of Scya2.

Inhibition of endotoxin-induced macrophage chemokine production by VIP and PACAP in vitro and in vivo

Inflammatory chemokines recruit immune cells which initiate and maintain the inflammatory response. Although such a response is necessary for the elimination of the antigen, the inflammation has to be eventually resolved. Peptides such as vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP), released following antigenic stimulation, contribute to the termination of an inflammatory response primarily by inhibiting the production of proinflammatory cytokines. Here we investigated the effects of VIP and PACAP on chemokine production. We report that VIP and PACAP inhibit the expression of the macrophage-derived CXC chemokines MIP-2 and KC (IL-8), and of the CC chemokines MIP-1a, MIP-1b, MCP-1 and RANTES in vivo and in vitro. The decrease of chemokine gene expression correlates with an inhibitory effect of VIP/PACAP on NFkB binding. In an in vivo model of acute peritonitis, the inhibition of chemokine production by VIP/PACAP leads to a significant reduction in the recruitment of PMNs, macrophages and lymphocytes into the peritoneal cavity. These findings support the proposed role of VIP and PACAP as key endogenous anti-inflammatory agents, and describe a novel mechanism, i.e., the inhibition of the production of macrophage-derived chemokines.

Inhibition of endotoxin-induced macrophage chemokine production by vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide in vitro and in vivo

Inflammatory chemokines recruit various populations of immune cells that initiate and maintain the inflammatory response against foreign Ags. Although such a response is necessary for the elimination of the Ag, the inflammation has to be eventually resolved in a healthy organism. Neuropeptides such as vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP), released after antigenic stimulation, contribute to the termination of an inflammatory response primarily by inhibiting the production of proinflammatory cytokines. Here we investigated the effects of VIP and PACAP on chemokine production. We report that VIP and PACAP inhibit the expression of the macrophage-derived CXC chemokines macrophage inflammatory protein-2 and KC (IL-8), and of the CC chemokines MIP-1alpha, MIP-1beta, monocyte chemoattractant protein 1, and RANTES in vivo and in vitro. The inhibition of chemokine gene expression correlates with an inhibitory effect of VIP/PACAP on NF-kappaB binding and transactivating activity. The VIP/PACAP inhibition of both chemokine production and of NF-kappaB binding and transactivating activity is mediated through the specific VIP receptor VPAC1, and involves both cAMP-dependent and -independent intracellular pathways. In an in vivo model of acute peritonitis, the inhibition of chemokine production by VIP/PACAP leads to a significant reduction in the recruitment of polymorphonuclear cells, macrophages, and lymphocytes into the peritoneal cavity. These findings support the proposed role of VIP and PACAP as key endogenous anti-inflammatory agents and describe a novel mechanism, i.e., the inhibition of the production of macrophage-derived chemokines.

Viral haemorrhagic septicaemia virus induces vig-2, a new interferon-responsive gene in rainbow trout

An mRNA differential display methodology was used to study the rainbow trout response to viral infection. A new transcript (vig-2) induced by viral haemorrhagic septicaemia virus (VHSV) in rainbow trout leucocytes was identified from the head-kidney. vig-2 was also induced in vivo during experimental infection and following DNA immunisation with a plasmid containing a gene encoding the viral glycoprotein. Viral induction of vig-2 was blocked by cycloheximide (CHX), indicating its dependency on a newly synthesised intermediate protein. This intermediate protein is most probably related to interferon because treatment of cells with a conditioned medium displaying an interferon-like activity resulted in a strong vig-2 expression, which was not blocked by CHX treatment. The cDNA sequence of the vig-2 transcript displays several mRNA destabilisation motifs and two signals characteristic of immediate-early gene expression. Curiously, vig-2 has no evident encoding potential except for a small 51 amino acid putative polypeptide with no clear similarity to any sequence available in the databanks. Therefore, the complete vig-2 genomic sequence was determined from a lambda phage clone retrieved from a genomic DNA library of rainbow trout. The genomic organisation of vig-2 shows five exons delimited with typical splice acceptor and donor sites. A promoter with a canonical ISRE, confirming that vig-2 is an interferon-responsive gene, is also present 115 nt upstream of the first exon.

Evidence for epigenetic mechanisms that silence both basal and immune-stimulated transcription of the IL-8 gene

It is becoming increasingly clear that epigenetic silencing of gene transcription plays a critical role in the regulation of gene expression in many biological processes. Tight regulation of immunomodulatory substances that are important for the initiation of the inflammatory cascade, such as chemoattractive cytokines, is essential to prevent initiation of unrestrained immune activation. Using the Caco-2 intestinal cell line as a model, we reveal two distinctly different mechanisms by which the gene for the neutrophil chemoattractive cytokine IL-8 is silenced. Nuclear run-on studies, as well as stably transfected reporter and marked minigene constructs, demonstrate that cellular differentiation inhibits immune-activated transcription of the IL-8 gene, a mechanism that is dependent on histone deacetylase activity. Unexpectedly, this silencing mechanism does not involve previously described regulatory elements in the IL-8 promoter but rather cis-acting regions located at a distance from the IL-8 gene locus. Genomic elements distant to the immediate IL-8 locus are also required to silence aberrant basal transcriptional activity of the IL-8 promoter in the absence of immune activation. However, in this case, silencing occurs in a histone deacetylase-independent fashion. These findings were confirmed in transgenic mice in which, in the absence of these elements, aberrant IL-8 gene activity was present primarily in the intestinal tract. Epigenetic silencing of cytokine gene transcription through distant genomic elements is an important level of gene regulation that may be relevant to the pathogenesis of immunologic disease states.

Low-Level Monocyte Chemoattractant Protein-1 Stimulation of Monocytes Leads to Tumor Formation in Nontumorigenic Melanoma Cells

Tumors commonly produce chemokines for recruitment of host cells, but the biological significance of tumor-infiltrating inflammatory cells, such as monocytes/macrophages, for disease outcome is not clear. Here, we show that all of 30 melanoma cell lines secreted monocyte chemoattractant protein-1 (MCP-1), whereas normal melanocytes did not. When low MCP-1-producing melanoma cells from a biologically early, nontumorigenic stage were transduced to overexpress the MCP-1 gene, tumor formation depended on the level of chemokine secretion and monocyte infiltration; low-level MCP-1 secretion with modest monocyte infiltration resulted in tumor formation, whereas high secretion was associated with massive monocyte/macrophage infiltration into the tumor mass, leading to its destruction within a few days after injection into mice. Tumor growth stimulated by monocytes/macrophages was due to increased angiogenesis. Vessel formation in vitro was inhibited with mAbs against TNF-alpha, which, when secreted by cocultures of melanoma cells with human monocytes, induced endothelial cells under collagen gels to form branching, tubular structures. These studies demonstrate that the biological effects of tumor-derived MCP-1 are biphasic, depending on the level of secretion. This correlates with the degree of monocytic cell infiltration, which results in increased tumor vascularization and TNF-alpha production.

Regulation of monocyte chemoattractant protein (MCP)-1 transcription by interferon-gamma (IFN-gamma) in human astrocytoma cells: postinduction refractory state of the gene, governed by its upstream elements

Monocyte chemoattractant protein (MCP)-1 is expressed by astrocytes in diverse inflammatory states and is a key regulator of monocyte recruitment to the central nervous system (CNS). In the current study, we addressed mechanisms by which transcription of the human MCP-1 gene (hMCP-1) was terminated, after induction by interferon (IFN)-gamma. Our results demonstrated that IFN-gamma-induced transcription of hMCP-1 was followed by a refractory state, during which hMCP-1 was resistant to restimulation by either IFN-gamma or heterologous activators such as TNF-alpha. This refractory state affected the hMCP-1 gene selectively, as other IFN-gamma-inducible genes remained responsive to restimulation. The IFN-gamma-induced hMCP-1 refractory state was governed at the transcriptional level and was sensitive to protein synthesis inhibitors, suggesting a requirement for newly expressed components. A minimal 213 base pair hMCP-1 regulatory element directed both IFN-gamma-mediated transcription and the subsequent refractory state. We previously demonstrated that IFN-gamma treatment resulted in coordinate protein occupancy in vivo of two hMCP-1 promoter elements, a gamma-activated site (GAS) and a GC-rich element. During the refractory state, IFN-gamma treatment failed to induce protection of either the hMCP-1 GAS element or the GC box. These results furnish insight into the expression of hMCP-1 during CNS inflammation and provide the first delineation of an IFN-gamma-induced transcriptional refractory state.

Molecular cloning and characterization of a novel regulator of G-protein signaling from mouse hematopoietic stem cells

A novel regulator of G-protein signaling (RGS) has been isolated from a highly purified population of mouse long-term hematopoietic stem cells, and designated RGS18. It has 234 amino acids consisting of a central RGS box and short divergent NH(2) and COOH termini. The calculated molecular weight of RGS18 is 27,610 and the isoelectric point is 8.63. Mouse RGS18 is expressed from a single gene and shows tissue specific distribution. It is most highly expressed in bone marrow followed by fetal liver, spleen, and then lung. In bone marrow, RGS18 level is highest in long-term and short-term hematopoietic stem cells, and is decreased as they differentiate into more committed multiple progenitors. The human RGS18 ortholog has a tissue-specific expression pattern similar to that of mouse RGS18. Purified RGS18 interacts with the alpha subunit of both G(i) and G(q) subfamilies. The results of in vitro GTPase single-turnover assays using Galpha(i) indicated that RGS18 accelerates the intrinsic GTPase activity of Galpha(i). Transient overexpression of RGS18 attenuated inositol phosphates production via angiotensin receptor and transcriptional activation through cAMP-responsive element via M1 muscarinic receptor. This suggests RGS18 can act on G(q)-mediated signaling pathways in vivo.

Site A of the MCP-1 distal regulatory region functions as a transcriptional modulator through the transcription factor NF1

The monocyte chemoattractant protein-1 (MCP-1) functions to recruit monocytes and macrophages to areas of inflammation and is a prototypic chemokine subjected to coordinate regulation by immunomodulatory agents. TNF mediated regulation of MCP-1 occurs through a distal regulatory region located 2.5 kb upstream of the transcriptional start site. Within this region are two NF-kB motifs that are each critical for function. Site A, located within the distal regulatory region and upstream of the kappaB elements is required for maximal induction by TNF. However, unlike the kappaB elements and other MCP-1 regulatory elements, Site A is constitutively occupied by factors in vivo. To better understand the nature of Site A function, this report identified a Site A binding protein and provides a functional analysis of the element in driving transcription. The results showed that the transcription factor NF1/CTF binds to Site A both in vitro and in vivo. While Site A has no transcriptional activity on its own, it was found to augment the transcriptional activity of a GAL4-VP16 reporter system in an orientation and position independent manner. Because NF1 is known to interact with factors that modify nucleosomes, these results suggest a unique role for Site A in regulating MCP-1 expression.

Differential transcriptional regulation of the monocyte-chemoattractant protein-1 (MCP-1) gene in tumorigenic and non-tumorigenic HPV 18 positive cells: the role of the chromatin structure and AP-1 composition

The expression of the monocyte-chemoattractant-protein-1 (MCP-1) is closely linked with a non-tumorigenic phenotype in somatic cell hybrids made between the human papillomavirus type 18 (HPV 18) positive cervical carcinoma cell line HeLa and normal human fibroblasts. In contrast, MCP-1 transcription is absent in tumorigenic segregants derived from the same hybrids or in parental HeLa cells. Selectivity of MCP-1 transcription, which is regulated at the level of initiation of transcription, is mainly based on differences in the location and extension of DNAse I-hypersensitive regions (DHSR) at both ends of the gene. While TNF-alpha only moderately increases the sensitivity of pre-existing 5'-DHSRs, a 3'-end DHSR became strongly induced exclusively in non-malignant hybrids. DNA sequencing showed that the 3'-DHSR coincides with an additional AP-1 site located approximately 600 bp downstream of the polyadenylation site. Analyses of AP-1 composition revealed that MCP-1 is only expressed in those cells where jun-family members were mainly heterodimerized with the fos-related protein fra-1. In contrast, in tumorigenic cells the 1: 1 ratio between jun and fra-1 is disturbed and the MCP-1 gene is no longer expressed. Hence, alterations in the heterodimerization pattern of AP-1 and its selective accessibility to opened chromatin may represent a novel regulatory pathway in the regulation of chemokines in malignant and non-malignant HPV-positive cells.

Cell to cell interaction between mesangial cells and macrophages induces the expression of monocyte chemoattractant protein-1 through nuclear factor-kappaB activation

The interaction between mesangial cells (MCs) and monocytes/macrophages (Mo/Mo) is an important pathogenic feature of glomerulonephritis. However, its mechanism is not fully elucidated. Studies to date have focused on the interactions through mediators. In the present study, to obtain insight into the mechanism of the interaction between MCs and Mo/Mo, we examined the significance of the cell to cell interaction of these cells in the context of monocyte chemoattractant protein-1 (MCP-1) expression using cell contact cultures or co-culture without contact. Our results revealed that the cellular adhesion of cultured macrophages to MCs induced the expression of MCP-1, which was mainly observed in the MCs. In addition, the induction of MCP-1 was, at least in part, mediated by nuclear factor kappa-B activation which occurs preferentially in the MCs. Because MCP-1 is suggested to play an important role in glomerulonephritis, this novel cell to cell interaction between the MCs and Mo/Mo could be important in glomerulonephritis.

trans-Retinoic acid blocks platelet-derived growth factor-BB-induced expression of the murine monocyte chemoattractant-1 gene by blocking the assembly of a promoter proximal Sp1 binding site

Proper regulation of the CC chemokine MCP-1 (monocyte chemoattractant protein-1) is important for normal inflammatory responses. MCP-1 is regulated by a wide variety of agents, including platelet-derived growth factor-BB (PDGF-BB) and tumor necrosis factor-alpha (TNF). Using both in vivo and in vitro assays, the elements required for expression between these two cytokines were compared. In vivo genomic footprinting showed that PDGF-BB induction occurred through the occupancy of the proximal regulatory region, and unlike TNF induction, no changes in the NF-kappaB binding, distal regulatory region occurred. Treatment of cells with trans-retinoic acid, an inhibitor of PDGF-BB activity, resulted in a 50% reduction in PDGF-BB-mediated induction and a concomitant block in the assembly of the proximal regulatory region. trans-Retinoic acid had minimal effect on TNF induction or promoter occupancy. An inhibitor of histone deacetylation was found to stimulate expression of MCP-1 in a manner that correlated with increased accessibility to the proximal regulatory region. These results show that the mechanisms of PDGF-BB and TNF activation of MCP-1 are distinct, although they both require the proximal regulatory region Sp1 binding site. The results also suggest that part of the mechanism used by both of these cytokines involves a process that regulates transcription factor access to the regulatory regions.

Platelet-derived growth factor stimulation of monocyte chemoattractant protein-1 gene expression is mediated by transient activation of the phosphoinositide 3-kinase signal transduction pathway

Platelet-derived growth factor (PDGF) stimulates transcription of an immediate-early gene set in Balb/c 3T3 cells. One cohort of these genes, typified by c-fos, is induced within minutes following activation of PDGF receptors. A second cohort responds to PDGF only after a significant time delay, although induction is still a primary response to receptor activation as shown by "superinduction" in the presence of the protein synthesis inhibitor cycloheximide. PDGF-receptor activated signaling pathways for the "slow" immediate-early genes are poorly resolved. Using gain-of-function mutations together with small molecule inhibitors of kinase activity, we show that activation of PI 3-kinase is both necessary and sufficient for the induction of the prototype slow immediate-early gene, monocyte chemoattractant-1 (MCP-1). Following activation of PDGF receptors, MCP-1 mRNA does not begin to accumulate for at least 90 min. However, only a brief (10 min) interval of PI 3-kinase activity is required to trigger this delayed response. The serine/threonine protein kinase, Akt/PKB, likely functions as a downstream affector of PI 3-kinase for this induction.

Cloning and characterization of the gene encoding mouse osteoclast differentiation factor

Osteoclast differentiation factor (ODF), a ligand for osteoclastogenesis inhibitory factor (OCIF)/ osteoprotegerin (OPG), is a member of the membrane-associated tumor necrosis factor (TNF) family and induces osteoclast-like cell formation in vitro. In the present study, mouse ODF genomic clones were isolated and sequenced to determine their gene structure. The mouse ODF gene is a single copy gene consisting of five exons and spans approximately 40kb of the mouse genome. The first exon encodes the intracellular and transmembrane domains. The extracellular region of ODF containing the TNF homologous domain is encoded by exons 1 through 5. The translation-termination codon and six polyadenylation signal residues are present in exon 5. A major transcription-initiation site is present 143 nucleotides upstream of the initiation-ATG codon. This genomic organization is similar to that of other members of the TNF family, especially the CD40 ligand.

Identification of an IL-8 homolog in lamprey (Lampetra fluviatilis): early evolutionary divergence of chemokines

Subtractive hybridization was used to study river lamprey (Lampetra fluviatilis) leukocyte-specific cDNA. A clone representing the most abundant component (12%) of the leukocyte library subtracted with liver cDNA was isolated and characterized. The cDNA encodes a presumably secreted polypeptide of 101 residues. The 3' untranslated region of the cDNA contains motifs characteristic of the transiently expressing genes. Comparison of the deduced amino acid sequence with known protein sequences revealed its homology to the members of the chemokine superfamily. Designated as LFCA-1, the lamprey protein contains four conserved cysteines, of which the first two are separated by a residue, and a number of other CXC family characteristic residues. LFCA-1 has the highest similarity to the chicken EMF-1 (40%) and to the mammalian IL-8 (32-33%). However, it lacks the ELR motif essential for the function of the mammalian IL-8-related chemokines. Based on the phylogenetic analysis of the LFCA-1 relationship to the higher vertebrate chemokines, it is concluded that the evolutionary origin of the chemokine superfamily is ancient, and that the divergence of the CXC and CC families most likely occurred at the time or before the first vertebrates emerged.

Platelet-derived growth factor-specific regulation of the JE promoter in rat aortic smooth muscle cells

JE is a member of the family of "immediate early" genes induced by growth factors and cytokines. JE encodes a low molecular weight secretory glycoprotein analogous to the human monocyte chemoattractant protein, MCP-1. JE and MCP-1 proteins are thought to play an important role in inflammation and in the recruitment of monocyte/macrophages to the vessel wall during the development of atherosclerosis. We have previously reported that the induction of JE in rat aortic smooth muscle cells (SMC) was specific to platelet-derived growth factor (PDGF) and was not seen with other growth agonists. Using a luciferase reporter system and transient transfection assays of rat aortic SMC, we now report the identification of a region in the proximal rat JE promoter that is responsive to PDGF but not to other growth factors (angiotensin II and alpha-thrombin) or cytokines (interleukin 1-beta and tumor necrosis factor-alpha). The full response to PDGF (approximately 6-fold) requires the cooperative activity of two potentially novel cis-acting elements, at positions -146 to -128 and -84 to -59. While each element produces a different pattern in electrophoretic mobility shift assays, they appear to bind the same PDGF-responsive species. Further analysis of these regions should provide important insights into PDGF-specific responses in vascular SMC.

Up-regulated expression of murine Mcl1/EAT, a bcl-2 related gene, in the early stage of differentiation of murine embryonal carcinoma cells and embryonic stem cells

We have cloned a murine homologue of the human Mcl1/EAT gene, a Bcl-2 related gene. Sequence analysis revealed that murine Mcl1/EAT (mMcl1/EAT) has three Bcl-2 homology domains, two PEST sequences, and immediate response boxes (IRB). The presence of IRB indicates that mMcl1/EAT is an immediate-early gene. mMcl1/EAT increases dramatically with exposure to retinoic acid in murine embryonal carcinoma cell lines (F9 and PCC3) as well as embryonic stem cells, both of which are models of early embryogenesis.

Expression and processing of G0/G1 switch gene 24 (G0S24/TIS11/TTP/NUP475) RNA in cultured human blood mononuclear cells

The human G0/G1 switch (G0S) gene, G0S24, and its rodent immediate-early homolog (TIS11, TTP, NUP475) are part of a mammalian gene family whose members encode CCCH zinc finger domains and domains similar to part of the large subunit of RNA polymerase II and to the Mei2 regulator of G1 arrest in fission yeast. We compared the RNA expression of G0S24 with that of other G0S genes in cultured blood mononuclear cells and examined the levels of various RNA processing intermediates. Freshly isolated cells contained high levels of several G0S RNAs, which declined by 24 h, suggesting transient spontaneous stimulation during cell purification (Heximer et al., 1996). However, in cells preincubated for 24 h, G0S24 RNA levels remained much higher than those of other G0S genes (107+/-42 x 10(6) molecules/microg of RNA); stimulation with lectin (Con-A) further increased G0S24 RNA, much of which remained nuclear. Like those of FOS/G0S7, EGR1/G0S30 and of the gene encoding the regulator of G protein signalling 1 (RGS1), G0S24 RNA levels increased more in response to a protein kinase C activator than to a calcium ionophore, whereas the opposite held for FOSB/G0S3 and RGS2/G0S8. With appropriate PCR primer pairs, we showed a G0S24 RNA processing intermediate, which crossed the exon-1/intron boundary, and nonpolyadenylated nuclear RNA extending into the 3' flank, where there is a second CpG island. The concentration of the latter intermediate (1.2+/-0.2 x 10(6) molecules/microg of RNA), which increased transiently on cell stimulation, did not account for all G0S24 nuclear RNA. The levels of G0S24 RNA and both intermediates were increased by the protein synthesis inhibitor cycloheximide, consistent with regulation by a labile repressor.

Abnormalities in monocyte recruitment and cytokine expression in monocyte chemoattractant protein 1-deficient mice

Monocyte chemoattractant protein 1 (MCP-1) is a CC chemokine that attracts monocytes, memory T lymphocytes, and natural killer cells. Because other chemokines have similar target cell specificities and because CCR2, a cloned MCP-1 receptor, binds other ligands, it has been uncertain whether MCP-1 plays a unique role in recruiting mononuclear cells in vivo. To address this question, we disrupted SCYA2 (the gene encoding MCP-1) and tested MCP-1-deficient mice in models of inflammation. Despite normal numbers of circulating leukocytes and resident macrophages, MCP-1(-/-) mice were specifically unable to recruit monocytes 72 h after intraperitoneal thioglycollate administration. Similarly, accumulation of F4/80+ monocytes in delayed-type hypersensitivity lesions was impaired, although the swelling response was normal. Development of secondary pulmonary granulomata in response to Schistosoma mansoni eggs was blunted in MCP-1(-/-) mice, as was expression of IL-4, IL-5, and interferon gamma in splenocytes. In contrast, MCP-1(-/-) mice were indistinguishable from wild-type mice in their ability to clear Mycobacterium tuberculosis. Our data indicate that MCP-1 is uniquely essential for monocyte recruitment in several inflammatory models in vivo and influences expression of cytokines related to T helper responses.

Multiple transcriptional variants and RNA editing in C18orf1, a novel gene with LDLRA and transmembrane domains on 18p11.2

C18orf1 is a novel brain-expressed transcript, mapping to 18p11.2. Upon further characterization, we found multiple and differentially expressed transcriptional variants. C18orf1 alpha 1, an 8.5-kb transcript, was predicted to code for a 306-amino-acid protein and a 7.1-kb 3'-untranslated region (UTR). This variant was encoded by at least six exons. Alternative transcripts included alpha 2, identical to alpha 1 but missing 18 residues, and N-terminal-truncated variants termed beta 1 and beta 2. A motif search suggested the presence of a transmembrane domain in both alpha and beta and a low-density lipoprotein receptor class A (LDLRA) domain in the alpha-specific N-terminal. In LDLR, LDLRA has been shown to be involved in binding Ca2+ and LDL, raising the possibility that C18orf1 might bind Ca2+ and an unknown ligand. We also present evidence of RNA editing in the 5'-UTR of beta 2, the first demonstration of this phenomenon in 5'-UTR.

Transcriptional regulation of the human monocyte chemoattractant protein-1 gene. Cooperation of two NF-kappaB sites and NF-kappaB/Rel subunit specificity

Human monocyte chemoattractant protein-1 (human MCP-1) mRNA accumulated in THP-1 cells 2 h after lipopolysaccharide (LPS) stimulation. DNase I footprinting revealed that LPS stimulation induced protein binding to the two closely located NF-kappaB sites, A1 and A2. By electrophoretic gel mobility shift assay and supershift assay, the binding of (p65)2, c-Rel/p65, p50/p65, and p50/c-Rel to the A2 oligonucleotide probe was detected after LPS stimulation. In contrast, 12-o-tetradecanoylphorbol 13-acetate did not induce a significant amount of MCP-1 mRNA in THP-1 cells 2 h after stimulation, and only p50/p65 bound to the A2 probe. trans-Activity of each NF-kappaB/Rel dimer was investigated by transfecting P19 cells with p65, p50, and/or c-Rel expression vectors, and a luciferase construct containing the enhancer region of the human MCP-1 gene. Expression of recombinant p65 or p65 and c-Rel resulted in elevated luciferase activities, indicating that (p65)2 and c-Rel/p65 had trans-activity. The binding of (p65)2 and/or c-Rel/p65 to the A2 probe was also detected from 12-o-tetradecanoylphorbol 13-acetate-stimulated HeLa, HOS, and A172 cells in which expression of MCP-1 mRNA was elevated. Finally, the role of the A1 site was investigated. Both (p65)2 and c-Rel/p65 bound to the A1 probe by electrophoretic mobility shift assay and a mutation in the A1 or A2 site resulted in a loss of the enhancer activity. These results suggest that the binding of (p65)2 and c-Rel/p65 to the A1 and A2 sites of this gene is important for the tissue- and stimulus-specific transcription of the human MCP-1 gene.

Identification of inflammatory mediators by screening for glucocorticoid-attenuated response genes

We describe an approach for identifying novel inflammatory mediators, based on screening for immediate early/primary response genes whose induction by an inflammatory stimulus is attenuated by glucocorticoids. This procedure can be applied to a wide range of cell types and tissues, using a variety of inducers. In an initial test of this idea, we identified cDNAs for 12 LPS-induced, glucocorticoid-attenuated response genes (GARGs) by differential hybridization screening of a lambda phage cDNA library from murine 3T3 fibroblasts. Seven of the GARGs were known genes, including the chemokines JE/MCP-1, fic/MARC/MCP-3, and crg2/IP-10. One of the novel cDNAs was a new C-X-C chemokine that we designated LIX, for LPS-induced C-X-C chemokine. Because the 12 GARG cDNAs were identified in a single screening of only 15,000 phage, and four were found as single isolates, these results suggest that there are many GARGs not yet described. Furthermore, six of the seven known GARGs encode proteins that modulate intercellular communication. These results support our hypothesis that GARGs predominantly encode products that function in paracrine cell communication. Here we provide an overview of the GARG strategy and the differential hybridization procedures used in our initial screening. A variety of other methods for identifying differentially expressed genes may be used in future searches for novel GARGs.

Characterization of a KRAB family zinc finger gene, ZNF195, mapping to chromosome band 11p15.5

We report the cDNA sequence of the zinc finger gene, ZNF195, which maps to chromosome 11p15.5. ZNF195 contains an N-terminal KRAB domain and 14 tandemly repeated Krüppel type zinc finger motifs at its C-terminus. Northern analysis shows expression of ZNF195 in adult heart, brain, placenta, skeletal muscle, and pancreas with a predominant transcript size of 4.3 kb. There is little expression in adult lung, liver, and kidney. In fetal lung, liver, kidney, and brain, the predominant transcript is 3.5 kb. Fetal brain also expresses a 4.3-kb transcript. RT-PCR analysis shows that two exons, 4a, which contains an inverted Alu sequence, and 4b, are differentially spliced and absent from the major transcript.

Serum- and polypeptide growth factor-inducible gene expression in mouse fibroblasts

Complex cellular processes such as proliferation, differentiation, and apoptosis are regulated in part by extracellular signaling molecules: for example, polypeptide growth factors, cytokines, and peptide hormones. Many polypeptide growth factors exert their mitogenic effects by binding to specific cell surface receptor protein tyrosine kinases. This interaction triggers numerous biochemical responses, including changes in phospholipid metabolism, the activation of a protein phosphorylation cascade, and the enhanced expression of specific immediate-early, delayed-early, or late response genes. In this review, I summarize the major findings obtained from studies investigating the effects of serum or individual polypeptide growth factors on gene expression in murine fibroblasts. Several experimental approaches, including differential hybridization screening of cDNA libraries and differential display, have been employed to identify mRNA species that are expressed at elevated levels in serum- or polypeptide growth factor-stimulated cells. These studies have demonstrated that serum- and growth factor-inducible genes encode a diverse family of proteins, including DNA-binding transcription factors, cytoskeletal and extracellular matrix proteins, metabolic enzymes, secreted chemokines, and serine-threonine kinases. Some of these gene products act as effectors of specific cell cycle functions (e.g., enzymes involved in nucleotide and DNA synthesis), others are required to successfully convert a metabolically inactive cell to a metabolically active cell that will eventually increase in size and then divide (e.g., glucose-metabolizing enzymes), and some actually function as positive or negative regulators of cell cycle progression. In conclusion, research conducted during the past 15 years on serum- and growth factor-regulated gene expression in murine fibroblasts has provided significant insight into mitogenic signal transduction and cell growth control.

Comparison of mRNA expression of two regulators of G-protein signaling, RGS1/BL34/1R20 and RGS2/G0S8, in cultured human blood mononuclear cells

RGS1 and RGS2 are members of a new class of regulators of G-protein signaling identified by their selective mRNA expression either in phorbol ester (TPA)-stimulated human B lymphocytes (RGS1/1R20/BL34) or in blood mononuclear cells treated with the T-cell lectin concanavalin A (ConA) and cycloheximide (RGS2/G0S8). The RGS1 gene shows low basal mRNA expression in freshly purified blood mononuclear cells, which increases upon incubation for a day. In contrast, RGS2 initially shows high basal levels of mRNA expression, which subsequently decrease. Expression of both genes increases in response to ConA, with RGS2 mRNA levels increasing briskly to a maximum between 0.5 and 1 hr and decreasing to baseline by 6 hr, whereas the RGS1 mRNA increase is delayed reaching a maximum between 1 and 2 hr. RGS1 mRNA levels increase much more in response to a protein kinase C activator (TPA), than to a calcium ionophore (ionomycin), whereas the opposite is true for RGS2. We suggest that ConA elevates RGS2 on the basis of its ability to increase intracellular calcium, and that RGS2 may be involved in the regulation of intracellular calcium. The distinction between RGS1 and RGS2 is further emphasized by studies indicating that recombinant RGS2 does not bind in vitro to two members of the G(i) subfamily of G-protein alpha-subunits for which recombinant RGS1 has high affinity.

Estrogens and atherosclerosis

Estrogens prevent heart disease in women and have also been shown to retard atherogenesis in animal models. Estrogens may act at several steps in the atherogenic process to prevent cardiovascular disease. Some of the benefits of estrogens can be ascribed to their ability to favorably alter the lipoprotein profile, i.e. increase high-density lipoprotein and decrease low-density lipoprotein, and also to their ability to prevent oxidative modification of low-density lipoprotein. Other beneficial effects of estrogens include direct actions on the vascular endothelium and vascular smooth muscle, leading to a decrease in the expression of adhesion molecules involved in monocyte adhesion to endothelial cells, and to a decrease in certain chemokines involved in monocyte migration into the subendothelial space. Estrogens may also affect the later stages of atherogenesis. Finally, estrogens may modify the behavior of atherosclerotic vessels by altering their reactivity and thereby promoting vasodilation, and this may also partly account for their ability to prevent clinical events due to cardiovascular disease.

Platelet-derived growth factor induction of the immediate-early gene MCP-1 is mediated by NF-kappaB and a 90-kDa phosphoprotein coactivator

A broad panel of agents including serum, interleukin-1, double-stranded RNA, and platelet-derived growth factor (PDGF) stimulate transcription of the "slow" immediate-early gene MCP-1. These disparate inducers act through a tight cluster of regulatory elements in the distal 5'-flanking sequences of the MCP-1 gene. We describe a 22-base element in this cluster which, in single copy, confers PDGF-inducibility to a tagged MCP-1 reporter gene. In mobility shift assays, the element binds a PDGF-activated form of NF-kappaB, and a 90-kDa protein (p90) which binds constitutively. Antibody supershift and UV cross-linking experiments indicate that the PDGF-activated NF-kappaB species is a Rel A homodimer. The DNA binding form of p90 is a nuclear-restricted serine/threonine phosphoprotein. Mutagenesis of the 22-base element shows that the NF-kappaB and p90 binding sites overlap, but binding of the two species is mutually independent. Both sites, however, are required for optimum PDGF induction of MCP-1. Therefore, p90 appears to be a coactivator with NF-kappaB in PDGF-mediated induction of MCP-1.

Activation of the gene encoding decay accelerating factor following nerve growth factor treatment of sensory neurons is mediated by promoter sequences within 206 bases of the transcriptional start site

Using two independent differential screening procedures designed to identify novel mRNAs induced by nerve growth factor (NGF) treatment of adult dorsal root ganglion (DRG) neurons, we have isolated cDNA clones derived from the gene encoding decay accelerating factor (DAF). Hybridization analysis and semi-quantitative polymerase chain reaction confirmed that the DAF mRNA was indeed induced in NGF-treated adult DRG neurons. Moreover, the DAF gene promoter is NGF inducible (approximately two- to threefold) when transfected into DRG neurons, and this effect is primarily dependent on sequences between -206 and -77 relative to the transcriptional start site. Hence, the DAF gene constitutes a novel NGF-inducible gene whose mRNA is elevated in response to NGF treatment of DRG neurons. The potential significance of this effect is discussed in terms of the role of NGF in modulating the transcriptional activity and function of adult DRG neurons.

The bradykinin B2 receptor is a delayed early response gene for platelet-derived growth factor in arterial smooth muscle cells

Bradykinin and platelet-derived growth factor (PDGF) are inflammatory mediators important in the response to vascular injury. Based upon the known effect of oncogenic Ras to increase bradykinin receptor expression and the ability of PDGF to stimulate Ras, we examined whether PDGF regulates bradykinin B2 receptor expression in cultured arterial smooth muscle cells. Treatment with PDGF (AB and BB, but not AA) produced a dose- and time-dependent increase in both mRNA (6-7-fold increase at 2-4 h) and cell surface receptors (2-4-fold at 6-12 h) for the B2 receptor. There was a 60-min delay between exposure to PDGF and the initial increase in B2 receptor mRNA. Transcriptional inhibitors, actinomycin D or 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole, completely blocked the increase in B2 receptor mRNA when added up to 60 min after stimulation with PDGF. However, protein synthesis was not required, as treatment with cycloheximide did not block but rather superinduced the PDGF-induced increase in B2 receptor mRNA. Comparison with the immediate early response gene c-fos demonstrated that the increase in B2 receptor mRNA was similarly inhibited by the tyrosine kinase inhibitor, tyrphostin, as well as staurosporine. However, stimulation of c-fos was slightly more sensitive to genistein, while the B2 receptor mRNA was more sensitive to inhibition by the protein kinase C inhibitor, calphostin C. The increase in cell surface B2 receptors were functionally coupled to an increase in phosphoinositide-specific phospholipase C, and the effects of PDGF were selective as there was no increase in either angiotensin II- or arginine vasopressin-induced inositol phosphate formation or intracellular calcium release. Taken together, these results demonstrate that the B2 receptor is a delayed early response gene for PDGF in vascular smooth muscle cells.

A localisation signal in the 3′ untranslated region of c-myc mRNA targets c-myc mRNA and beta-globin reporter sequences to the perinuclear cytoplasm and cytoskeletal-bound polysomes

There is increasing evidence that in mammalian cells some mRNAs are localised to specific parts of the cytoplasm and a proportion of mRNAs and polyribosomes are associated with the cytoskeleton. It has been shown previously that c-myc mRNA is present in the perinuclear cytoplasm and associated with the cytoskeleton, and that this localisation is dependent upon the 3′ untranslated region of the mRNA. The present studies show that in transfected fibroblasts the c-myc 3′ untranslated region is able to localise beta-globin reporter sequences to the perinuclear cytoplasm. Studies with constructs containing deletions within the 3′ untranslated region identify the region between bases 194 and 280 as critical for localisation. Transfection of cells with constructs in which this region is linked to beta-globin sequences showed that it was sufficient to localise the chimaeric transcripts to the perinuclear cytoplasm and to cytoskeletal-bound polyribosomes. Transfection with constructs containing a mutated AUUUA sequence within the 194–280 base region showed that this conserved AUUUA is required for targeting of both c-myc mRNA and a chimaeric transcript of beta-globin transcripts linked to the c-myc 3′ untranslated region. The region between bases 194 and 280 did not induce instability of beta-globin transcripts and the AUUUA mutation had little effect upon mRNA stability. We propose that this 86 nt region of the 3′ untranslated region contains a localisation signal to target c-myc mRNA so that it is retained on cytoskeletal-bound polysomes in the perinuclear cytoplasm; a conserved AUUUA sequence appears to be a critical part of this signal.

Isolation and characterization of xnov, a Xenopus laevis ortholog of the chicken nov gene

We have isolated an ortholog (xnov) of the chicken nov gene (for nephroblastoma overexpressed; encoding a putative avian proto-oncogene) from Xenopus laevis (Xl) by screening an Xl ovary cDNA library and genomic library using the entire coding region of human CTGF (encoding connective tissue growth factor) as a probe and by 5'RACE (rapid amplification of cDNA ends). xnov has the same genomic organization as chicken nov, mouse fisp12 and cyr61, but has a unique promoter sequence. The Xl open reading frame (ORF) encodes a 343-amino-acid (aa) polypeptide of 37.9 kDa. Xnov shows 62.9, 60.5, 52.2, 52.1, 47.6 and 45.8% identity with the chicken Nov, human NovH, human CTGF, mouse Fisp12, chicken Cef10 and mouse Cyr61 proteins, respectively. Xnov contains four aa domains which characterize the CTGF family. RT-PCR (reverse transcription-polymerase chain reaction) analysis shows that the xnov mRNA is very low in abundance and appears to be present throughout early Xl development. Our results also indicate that xnov and nov are not orthologs of human CTGF.

Stimulation by parathyroid hormone of interleukin-6 and leukemia inhibitory factor expression in osteoblasts is an immediate-early gene response induced by cAMP signal transduction

Parathyroid hormone and other agents that stimulate bone resorption function, at least in part, by inducing osteoblasts to secrete cytokines that stimulate osteoclast differentiation and activity. We previously demonstrated that parathyroid hormone induces expression by osteoblasts of interleukin-6 and leukemia inhibitory factor without affecting the 16 other cytokines that were examined. We also showed that stimulation of osteoclast activity by parathyroid hormone is dependent on activation of the cAMP signal transduction pathway and secretion of interleukin-6 by osteoblasts. In the current study, we demonstrate that the rapid and transient stimulation of interleukin-6 and leukemia inhibitory factor is inhibited by actinomycin D and superinduced by protein synthesis inhibitors, the classical characteristics of an immediate-early gene response. Moreover, activation of cAMP signal transduction by parathyroid hormone and parathyroid hormone-related protein is necessary and sufficient to induce both interleukin-6 and leukemia inhibitory factor. In addition, cAMP analogues as well as vasoactive intestinal peptide and isoproterenol, two neuropeptides that stimulate bone resorption by activating cAMP signal transduction in osteoblasts, also induce interleukin-6 and leukemia inhibitory factor in these cells. Taken together with our previous results, this study suggests that interleukin-6 is crucial for stimulation of bone resorption not only by parathyroid hormone, but also by parathyroid hormone-related protein, vasoactive intestinal peptide, and beta-adrenergic agonists, like isoproterenol.

Sex steroid hormones and macrophage function

Macrophages are versatile cells whose activities are programmed by environmental signals. In this review, we discuss the potential impact of sex steroid hormones on macrophage activation and production of various effector molecules. The evidence accumulated to date supports the postulate that estrogens, progesterone, androgens and testosterone profoundly influence host defense by controlling the ability of macrophages to participate in immune responses.

Transcriptional control and the regulation of endocrine genes

1. Endocrine genes are regulated at a number of levels during their expression. Regulation can occur during transcription, mRNA splicing, mRNA degradation, translation, or post-translational processing of protein precursors. 2. Transcription is controlled by an increasingly well studied and enlarging family of transcription factors that bind to basal control DNA sequences (promoters) and transcriptional activator sequences (enhancers). 3. Steroid receptors act as transcription factors, as do the proteins involved in the gene regulation by cyclic AMP. Parathyroid hormone related protein is typical of many endocrine genes in that it is regulated by multiple agonists including glucocorticoids and hormones activating the cyclic AMP cascade.

Transcriptional regulation of the rat insulin-like growth factor-I gene involves metabolism-dependent binding of nuclear proteins to a downstream region

Insulin-like growth factor-I (IGF-I) gene transcription is mediated largely via exon 1. In an initial search for regulatory regions, rat hepatocytes were transfected with IGF-I constructs. Since omission of downstream sequences led to reduced expression, we then used in vitro transcription to evaluate potential metabolic regulation via downstream regions. With templates including 219 base pairs of downstream sequence, transcriptional activity was reduced 70-90% with hepatic nuclear extracts from diabetic versus normal rats. However, activity was comparable with templates lacking downstream sequences. The downstream region contained six DNase I footprints, and templates with deletion of either region III or V no longer provided reduced transcriptional activity with nuclear extracts from diabetic rats. Nuclear protein binding to regions III and V appeared to be metabolically regulated, as shown by reduced DNase I protection and activity in gel mobility shift assays with nuclear extracts from diabetic rats. Southwestern blotting probes corresponding to regions III and V recognized a approximately 65-kDa nuclear factor present at reduced levels in diabetic rats. These findings indicate that a downstream region in exon 1 may be important for both IGF-I expression and metabolic regulation. Altered concentration or activity of a transcription factor(s) binding to this region may contribute to reduced IGF-I gene transcription associated with diabetes mellitus.

Glucocorticoid-attenuated response genes encode intercellular mediators, including a new C-X-C chemokine

A major part of the anti-inflammatory effect of glucocorticoids is attributable to their attenuation of the induction of genes whose products mediate intercellular interactions, e.g. cytokines and the inducible forms of prostaglandin synthase and nitric oxide synthase. We hypothesized that (i) there exists a class of immediate-early/primary response genes whose induction by inflammatory agents, mitogens, and other stimuli is attenuated by glucocorticoids, and (ii) the products of these glucocorticoid-attenuated response genes (GARGs) function predominantly in paracrine cell processes. We constructed a lambda cDNA library from transforming growth factor beta 1-pretreated murine Swiss 3T3 cells stimulated with lipopolysaccharide (LPS) or serum in the presence of cycloheximide, screened 15,000 plaques by differential hybridization, and cloned 12 LPS-induced, dexamethasone-attenuated cDNAs. Seven were previously known. Six of these encode intercellular mediators (thrombospondin-1, MCSF, JE/MCP-1, MARC/fic/MCP-3, crg2/IP-10, and cyr61); one encodes a protein of unknown function (IRG2). Thus, a large majority of these GARG cDNAs encode intercellular mediators, as hypothesized. Of the five GARG cDNAs not previously known, one encodes a novel member of the CXC chemokine family, designated LIX (LPS-induced CXC chemokine). The predicted LIX protein has a 40-amino acid signal sequence and a 92-amino acid mature peptide with a distinctive COOH-terminal region. Surprisingly, segments of the 3'-untranslated regions of LIX and two other CXC chemokines have substantially greater nucleotide sequence homology than do their coding regions. These segments may perform an unknown regulatory function. The LIX message is strongly induced by LPS in fibroblasts, but not in macrophages, suggesting that LIX may participate in the recruitment of inflammatory cells by injured or infected tissue.

Identification of a new enhancer in the promoter region of human TR3 orphan receptor gene. A member of steroid receptor superfamily

Human TR3 orphan receptor is a member of the steroid/thyroid hormone receptor superfamily and is the human homologue of the proteins encoded by the rat NGFI-B and mouse nur77 genes. These genes are induced rapidly by androgens/growth factors and may have functions related to cell proliferation, differentiation, and apoptosis. To investigate the TR3 orphan receptor gene transcriptional regulation, a 2.3-kilobase genomic DNA fragment containing the TR3 orphan receptor gene promoter region was isolated, sequenced, and characterized. Sequence homology search within this promoter region revealed some potential cis-acting elements such as cAMP response element, interleukin-6 response element, estrogen response element, and GC box. Deletion analysis and chloramphenicol acetyltransferase assay also showed a novel cis-acting element of TR3 orphan receptor gene (NCAE-TR3), 200-181 base pairs upstream of the transcriptional start site. Gel retardation assay further demonstrated that some nuclear factors can bind to this NCAE-TR3. Together, our data suggest that NCAE-TR3 could be a new enhancer element associated with the transcription of an early response gene for mitogenesis and apoptosis.

Parathyroid hormone-related protein

We review the current state of knowledge of the molecular properties and actions of parathyroid hormone-related protein (PTHrP) both in cancer patients and in normal physiology. PTHrP is a common product of squamous cancers and is the major mediator of the syndrome of humoral hypercalcemia of malignancy (HHM) by its actions through parathyroid hormone receptors in bone and kidney. Recently developed radioimmunoassays and tissue localization techniques indicate that PTHrP is produced by many more cancers than was originally indicated by clinical studies and that it contributes significantly to malignancy-related hypercalcemia associated with other etiologies, for example, cancers metastatic to bone and hematological malignancies. The gene encoding PTHrP is complex, with multiple exons coding for up to 12 alternate transcripts and three different length proteins, potentially in a tissue-specific manner, by the use of three promoters. Its expression is regulated by hormones and growth factors, and the untranslated exons display features in common with many cytokine genes. Although potential endocrine actions of PTHrP are evident in fetal development, further evidence suggesting that the normal physiological role of PTHrP is predominantly as a locally produced regulator/cytokine comes from localization studies and investigations of its actions in a variety of tissues. Such studies indicate that in addition to its parathyroid hormone-like actions, PTHrP has multiple activities, including those in fetal development, placental calcium transfer, lactation, smooth muscle relaxation, and on epithelial cell growth. Although PTHrP was discovered because of its production by cancers, evidence for its actions as a local regulator highlights the importance of understanding its roles not only in the etiology of HHM in cancer patients but also in normal tissues.

Structural organisation and chromosomal mapping of the human Id-3 gene

The helix-loop-helix (HLH) family of transcription factors plays a central role in the regulation of cell growth, differentiation and tumourigenesis. Members of the Id (inhibitor of DNA binding) class of these nuclear proteins are able to heterodimerise with and thereby antagonise the functions of other transcription factors of this family. We report here on the genomic organisation of the human Id3 (HLH 1R21/heir1) gene. Comparison with the two other mammalian Id genes, Id1 and Id2, reveals a highly conserved protein coding gene organisation consistent with evolution from a common, ancestral Id-like gene. In addition, by using a yeast artificial chromosome (YAC) clone of Id3, we have fine-scale mapped the gene to chromosome band 1p36.1 by fluorescence in situ hybridisation (FISH) and, using the same FISH technique, we have detected heterogeneity in tumour-associated 1p36 chromosome translocations.

Functional role of the cis-acting elements in human monocyte chemotactic protein-1 gene in the regulation of its expression by phorbol ester in human glioblastoma cells

The monocyte chemotactic protein-1 (MCP-1) is a 76 amino acid protein that specifically attracts monocytes. The expression of MCP-1 gene can be induced by lipopolysaccharides (LPS), phorbol esters (TPA) and several cytokines. However, how they regulate MCP-1 gene expression is not known. We tested whether the two putative TPA-responsive elements (TREs) and one kappa B enhancer-like region found in the MCP-1 promoter region, are involved in this regulation of MCP-1 gene expression. The 5' untranslated region of MCP-1 gene was linked to chloramphenicol acetyl transferase (CAT) reporter gene and transfected into human glioblastoma cells in which endogenous MCP gene expression was found to be stimulated by TPA and tumor necrosis factor-alpha (TNF-alpha). The 128 bp 5'-flanking region containing one TRE was adequate for basal promoter activity but the presence of both TREs in the MCP-1 promoter region were needed to give TPA responsive enhancement (2.5 fold) of expression of the marker gene. Mutations in either of the TRE's could abolish the TPA induction of CAT expression. Replacement of the kappa B enhancer-like element with a TRE-like sequence caused a 10-fold enhancement of CAT expression by TPA treatment. Random mutation of kappa B enhancer-like element did not affect CAT expression or its TPA induction. None of the MCP promoter constructs showed significant increase in CAT expression by treatment with tumor necrosis factor-alpha (TNF-alpha). This result suggested that the TNF regulation of MCP-1 gene involves other parts of the gene besides the proximal 5' flanking region.

Molecular structure and organization of the human manganese superoxide dismutase gene

Human manganese superoxide dismutase (MnSOD) is one of the major cellular defense enzymes that protects against toxic effects of superoxide radicals. Overexpression of human MnSOD has been shown to inhibit radiation-induced neoplastic transformation, suppress malignancy of cancer cells, and increase tolerance to various toxic agents. To elucidate the human MnSOD gene structure for identification of potential regulatory elements, we isolated five lambda clones from a normal human genomic DNA library and sequenced the largest clone containing the entire human MnSOD gene. The results demonstrated that human MnSOD is a single-copy gene consisting of five exons interrupted by four introns with typical splice junctions. A distinctive transcription initiation site was identified 74 bp upstream from the translation start site. This transcription initiation site is preceded by a G + C-rich (78%) promoter region containing a cluster of seven SP1 and three AP2 consensus sequences with no TATA box or CAAT box. The 3'-flanking region of the MnSOD gene contains one NF-kappa B consensus sequence. The presence of SP1, AP2, and NF-kappa B consensus sequences suggests that these potential regulatory elements may play a role in the regulation of human MnSOD gene expression.

Regulation of macrophage gene expression by T-cell-derived lymphokines

Cytokines secreted from antigen-specific T lymphocytes provide important positive and negative control of inflammation through their effects on non-antigen-specific inflammatory leukocytes. These effects often involve modulation of gene expression. Lymphokine-inducible macrophage gene expression is largely controlled at the level of transcription. Multiple cis-acting sequence motifs cooperate with one another to produce patterns of expression that are relatively unique to individual genes. Members of trans-acting transcription factor families, which recognize related regulatory sequence elements, participate frequently in complex protein-protein interactions that generate remarkable complexity in terms of the number of potential combinations and the consequential functional differences exhibited by each combination. Thus, the remarkable plasticity of immune-mediated inflammation derives from combinations of finite numbers of options at several points in the cellular and molecular sequence.