Isolation of the oncogene and epidermal growth factor-induced transin gene: complex control in rat fibroblasts

A glimpse of matrix metalloproteinases in diabetic nephropathy

Matrix metalloproteinases (MMPs) are proteolytic enzymes belonging to the family of zinc-dependent endopeptidases that are capable of degrading almost all the proteinaceous components of the extracellular matrix (ECM). It is known that MMPs play a role in a number of renal diseases, such as, various forms of glomerulonephritis and tubular diseases, including some of the inherited kidney diseases. In this regard, ECM accumulation is considered to be a hallmark morphologic finding of diabetic nephropathy, which not only is related to the excessive synthesis of matrix proteins, but also to their decreased degradation by the MMPs. In recent years, increasing evidence suggest that there is a good correlation between the activity or expression of MMPs and progression of renal disease in patients with diabetic nephropathy and in various experimental animal models. In such a diabetic milieu, the expression of MMPs is modulated by high glucose, advanced glycation end products (AGEs), TGF-β, reactive oxygen species (ROS), transcription factors and some of the microRNAs. In this review, we focused on the structure and functions of MMPs, and their role in the pathogenesis of diabetic nephropathy.

Cell-type-selective induction of c-jun by TAF4b directs ovarian-specific transcription networks

Cell-type-selective expression of the TFIID subunit TAF(II)105 (renamed TAF4b) in the ovary is essential for proper follicle development. Although a multitude of signaling pathways required for folliculogenesis have been identified, downstream transcriptional integrators of these signals remain largely unknown. Here, we show that TAF4b controls the granulosa-cell-specific expression of the proto-oncogene c-jun, and together they regulate transcription of ovary-selective promoters. Instead of using cell-type-specific activators, our findings suggest that the coactivator TAF4b regulates the expression of tissue-specific genes, at least in part, through the cell-type-specific induction of c-jun, a ubiquitous activator. Importantly, the loss of TAF4b in ovarian granulosa cells disrupts cellular morphologies and interactions during follicle growth that likely contribute to the infertility observed in TAF4b-null female mice. These data highlight a mechanism for potentiating tissue-selective functions of the basal transcription machinery and reveal intricate networks of gene expression that orchestrate ovarian-specific functions and cell morphology.

CIZ, a zinc finger protein that interacts with p130(cas) and activates the expression of matrix metalloproteinases

p130(cas) (Cas) is a docking protein that contains an SH3 domain and multiple tyrosine residues. p130(cas) is located at focal adhesions, is tyrosine phosphorylated in response to integrin stimulation, and is thought to transmit signals, via c-Crk and other proteins, for the remodeling of actin stress fibers and cell movement. In a search for the ligands of the SH3 domain of p130(cas) by far-Western screening, we cloned a novel protein named CIZ (for Cas-interacting zinc finger protein). CIZ consists of the following: a putative leucine zipper; a serine/threonine-rich region; a proline-rich sequence; five, six, or eight Krüppel-type C(2)H(2) zinc fingers; and the glutamine-alanine repeat. CIZ binds Cas in cells and is located in the nucleus and at focal adhesions. We showed that CIZ is a nucleocytoplasmic shuttling protein, by using the transient interspecies heterokaryon formation assay. In order to search for the targets of CIZ in nucleus, we determined the DNA binding consensus of CIZ as (G/C)AAAAA(A) by cyclic amplification and selection of targets analysis. The consensus-like sequences are found in several promoters of matrix metalloproteinases (MMPs), which are the enzymes used to degrade the extracellular matrix proteins. CIZ binds to a consensus-like sequence in the MMP-1 (collagenase) promoter. Overexpression of CIZ upregulates the transcriptions from MMP-1, MMP-3 (stromelysin), and MMP-7 (matrilysin) promoters, and this transactivation was enhanced in the presence of Cas. Furthermore, the stable overexpression of CIZ promoted the production of MMP-7 in culture medium. In summary, CIZ, a novel zinc finger protein, binds Cas, is a nucleocytoplasmic shuttling protein, and regulates the expression of MMPs.

Transcriptional regulation of stromelysin-1 gene expression is altered during progression of mouse mammary epithelial cells from functionally normal to malignant

The matrix metalloproteinase stromelysin-1 plays a central role during mammary gland development and tumor progression. To gain insight into the regulation of stromelysin-1 gene expression, the murine stromelysin-1 promoter was cloned and transfected into mouse mammary epithelial cells displaying various degrees of malignancy. A reconstituted basement membrane inhibited stromelysin-1 promoter activity in functionally normal cells, had little effect on moderately malignant cells and up-regulated the promoter in highly malignant cells. Spreading of normal and malignant cells was reduced by a reconstituted basement membrane, compared to a plastic substratum. Preventing spreading by maintenance of cells in suspension culture, regulated stromelysin-1 promoter activity in a manner similar to that on a reconstituted basement membrane. Conversely, increasing spreading by augmenting substratum adhesivity up-regulated stromelysin-1 promoter activity in tumor cells. In cells with reduced spreading in the presence of reconstituted basement membrane and in suspension culture, actin stress fibers were replaced by cortical actin bundles. In tumor cells, but not in functionally normal cells, treatment with phorbol diesters also resulted in accumulation of cortical actin and increased stromelysin-1 promoter activity. Consistent with an epithelial-to-mesenchymal conversion, regulation of stromelysin-1 gene expression in highly malignant cells was similar to its regulation in mammary fibroblasts. We conclude that the switch in transcriptional regulation of stromelysin-1 expression that occurs during epithelial-to-mesenchymal transition and conversion to tumorigenicity is related to altered regulation of signals from the cytoarchitecture.

Overexpression of a kinase-deficient transforming growth factor-beta type II receptor in mouse mammary stroma results in increased epithelial branching

Members of the transforming growth factor-beta (TGF-beta) superfamily signal through heteromeric type I and type II serine/threonine kinase receptors. Transgenic mice that overexpress a dominant-negative mutation of the TGF-beta type II receptor (DNIIR) under the control of a metallothionein-derived promoter (MT-DNIIR) were used to determine the role of endogenous TGF-betas in the developing mammary gland. The expression of the dominant-negative receptor was induced with zinc and was primarily localized to the stroma underlying the ductal epithelium in the mammary glands of virgin transgenic mice from two separate mouse lines. In MT-DNIIR virgin females treated with zinc, there was an increase in lateral branching of the ductal epithelium. We tested the hypothesis that expression of the dominant-negative receptor may alter expression of genes that are expressed in the stroma and regulated by TGF-betas, potentially resulting in the increased lateral branching seen in the MT-DNIIR mammary glands. The expression of hepatocyte growth factor mRNA was increased in mammary glands from transgenic animals relative to the wild-type controls, suggesting that this factor may play a role in TGF-beta-mediated regulation of lateral branching. Loss of responsiveness to TGF-betas in the mammary stroma resulted in increased branching in mammary epithelium, suggesting that TGF-betas play an important role in the stromal-epithelial interactions required for branching morphogenesis.

Expression of matrix metalloproteinases during rat skin wound healing: evidence that membrane type-1 matrix metalloproteinase is a stromal activator of pro-gelatinase A

Skin wound healing depends on cell migration and extracellular matrix remodeling. Both processes, which are necessary for reepithelization and restoration of the underlying connective tissue, are believed to involve the action of extracellular proteinases. We screened cDNA libraries and we found that six matrix metalloproteinase genes were highly expressed during rat skin wound healing. They were namely those of stromelysin 1, stromelysin 3, collagenase 3, gelatinase A (GelA), gelatinase B, and membrane type-1 matrix metalloproteinase (MT1-MMP). The expression kinetics of these MMP genes, the tissue distribution of their transcripts, the results of cotransfection experiments in COS-1 cells, and zymographic analyses performed using microdissected rat wound tissues support the possibility that during cutaneous wound healing pro-GelA and pro-gelatinase B are activated by MT1-MMP and stromelysin 1, respectively. Since MT1-MMP has been demonstrated to be a membrane-associated protein (Sato, H., T. Takino, Y. Okada, J. Cao, A. Shinagawa, E. Yamamoto, and M. Seiki. 1994. Nature (Lond.). 370: 61-65), our finding that GelA and MT1-MMP transcripts were expressed in stromal cells exhibiting a similar tissue distribution suggests that MT1-MMP activates pro-GelA at the stromal cell surface. This possibility is further supported by our observation that the processing of pro-GelA to its mature form correlated to the detection of MT1-MMP in cell membranes of rat fibroblasts expressing the MT1-MMP and GelA genes. These observations, together with the detection of high levels of the mature GelA form in the granulation tissue but not in the regenerating epidermis, suggest that MT1-MMP and GelA contribute to the restoration of connective tissue during rat skin wound healing.

Cellular transformation and malignancy induced by ras require c-jun

ras is an important oncogene in experimental animals and humans. In addition, activated ras proteins are potent inducers of the transcription factor AP-1, which is composed of heterodimeric complexes of Fos and Jun proteins. Together with the fact that deregulated expression of some AP-1 proteins can cause neoplastic transformation, this finding suggests that AP-1 may function as a critical ras effector. We have tested this hypothesis directly by analyzing the response to activated ras in cells that harbor a null mutation in the c-jun gene. The transcriptional response of AP-1-responsive genes to activated ras is severely impaired in c-jun null fibroblasts. Compared with wild-type cells, the c-jun null cells lack many characteristics of ras transformation, including loss of contact inhibition, anchorage independence, and tumorigenicity in nude mice; these properties are restored by forced expression of c-jun. Rare tumorigenic variants of ras-expressing c-jun null fibroblasts do arise. Analysis of these variants reveals a consistent restoration of AP-1 activity. The results provide genetic evidence that c-jun is a crucial effector for transformation by activated ras proteins.

Modulation of transforming growth factor beta receptor levels on microvascular endothelial cells during in vitro angiogenesis

Microvascular endothelial cells (RFCs) cultured in two-dimensional (2D) cultures proliferate rapidly and exhibit an undifferentiated phenotype. Addition of transforming growth factor beta1 (TGFbeta1) increases fibronectin expression and inhibits proliferation. RFCs cultured in three-dimensional (3D) type I collagen gels proliferate slowly and are refractory to the anti-proliferative effects of TGF beta1. TGF beta1 promotes tube formation in 3D cultures. TGF beta1 increases fibronectin expression and urokinase plasminogen activator (uPA) activity and plasminogen activator inhibitor-1 (PAI-1) levels in 3D cultures. Since the TGF beta type I and II receptors have been reported to regulate different activities induced by TGF beta1, we compared the TGF beta receptor profiles on cells in 2D and 3D cultures. RFCs in 3D cultures exhibited a significant loss of cell surface type II receptor compared with cells in 2D cultures. The inhibitory effect of TGF beta1 on proliferation is suppressed in transfected 2D cultures expressing a truncated form of the type II receptor, while its stimulatory effect on fibronectin production is reduced in both 2D and 3D transfected cultures expressing a truncated form of the type I receptor. These data suggest that the type II receptor mediates the antiproliferative effect of TGF beta1 while the type I receptor mediates the matrix response of RFCs to TGF beta1 and demonstrate that changes in the matrix environment can modulate the surface expression of TGF beta receptors, altering the responsiveness of RFCs to TGF beta1.

Degradation of endothelial cell matrix collagen is correlated with induction of stromelysin by an activated ras oncogene

A conditional expression system was established whereby the human K-ras, v-src, and v-mos genes were cloned into a conditional expression vector downstream of the dexamethasone-inducible mouse mammary tumor virus long terminal repeat. Rat-1 fibroblasts were transfected with these constructs and selected in medium containing G418. Cloned transfectants were isolated and characterized for absolute dependence on dexamethasone for expression of oncogene products and anchorage-independent growth in soft agar. Expression of activated p21K-ras(val12) enabled the fibroblasts to degrade extracellular matrix collagen secreted by murine microvessel endothelial cells. Concurrent with p21K-ras(val12) induction a proteinase with the characteristic size and substrate specificity of transin, the murine homologue of the human matrix metalloproteinase stromelysin, was expressed and secreted. Induction of v-mos and v-src oncogenes resulted in little or no detectable transin expression respectively coinciding with a relative or absolute failure to increase degradation of extracellular matrix collagen. This study suggests that in this system the expression of the ras oncogene can contribute to the in vitro invasive behavior of tumor cells by upregulating the production of a metalloproteinase capable of degrading collagen synthesized by vascular endothelial cells.

Defining a novel cis element in the 3'-untranslated region of mammalian ribonucleotide reductase component R2 mRNA: role in transforming growth factor-beta 1 induced mRNA stabilization

Ribonucleotide reductase R2 gene expression is elevated in BALB/c 3T3 fibroblasts treated with transforming growth factor beta 1. We investigated the possibility that the 3'-UTR of ribonucleotide reductase R2 mRNA contains regulatory information for TGF-beta 1 induced message stability. Using end-labeled RNA fragments in gel shift assays and UV cross-linking analyses, we detected in the 3'-UTR a novel 9 nucleotide (nt) cis element, 5'-GAGUUUGAG-3' site, which interacted specifically with a cytosolic protease sensitive factor to form a 75 kDa complex. The cis element protein binding activity was inducible and markedly up-regulated cross-link 4 h after TGF-beta 1 treatment of mouse BALB/c 3T3 cells. Other 3'-UTRs [IRE, GM-CSF, c-myc and homopolymer (U)] were poor competitors to the cis element with regard to forming the TGF-beta 1 dependent RNA-protein complex. However, the cis element effectively competed out the formation of the R2 3'-UTR protein complex. Cytosolic extracts from a variety of mammalian cell lines (monkey Cos7, several mouse fibrosarcomas and human HeLa S3) demonstrated similar TGF-beta 1 dependent RNA-protein band shifts as cell extract from BALB/c 3T3 mouse fibroblasts. Binding was completely prevented by several different mutations within the cis element, and by substitution mutagenesis, we were able to predict the consensus sequences, 5'-GAGUUUNNN-3' and 5'-NNNUUUGAG-3' for optimal protein binding. These results support a model in which the 9 nt region functions in cis to destabilize R2 mRNA in cells; and upon activation, a TGF-beta 1 responsive protein is induced and interacts with the 9 nt cis element in a mechanism that leads to stabilization of the mRNA. This appears to be the first example of a mRNA binding site that is involved in TGF-beta 1-mediated effects.

Cloning of a 72 kDa matrix metalloproteinase (gelatinase) from chicken embryo fibroblasts using gene family PCR: expression of the gelatinase increases upon malignant transformation

Chicken embryo fibroblasts secrete a 72 kDa progelatinase that displays all of the characteristics of a matrix metalloproteinase. Employing reverse-transcription PCR and degenerate oligonucleotide primers that are specific for two highly conserved sequences found in all matrix metalloproteinases, a DNA fragment specific for the chicken gelatinase was generated. Using this PCR product as a probe, cDNA clones were isolated from a chicken embryo cDNA library and the entire protein coding sequence was determined. The chicken progelatinase is 84% identical, at the amino acid level, with human and mouse 72 kDa progelatinase/type-IV procollagenase, with the greatest degree of similarity occurring in the propeptide and catalytic domains. The avian and mammalian proteinases diverge significantly in the C-terminal, hemopexin-like domain. The last 100 residues of the chicken gelatinase are only 66% identical with mammalian gelatinases. Mouse 72 kDa progelatinase, however, does not diverge significantly (> 98% identity) from human progelatinase in the hemopexin-like domain. The divergence in this domain of the chicken progelatinase may explain some of the distinct catalytic and inhibitory properties of the 72 kDa chicken progelatinase. Northern-blot analysis reveals that steady-state levels of the chicken progelatinase mRNA are increased 5-fold upon malignant transformation of chicken embryo fibroblasts with Rous sarcoma virus (RSV) and 3-fold by treatment with the tumour-promoting phorbol ester, phorbol 12-myristate 13-acetate (PMA). This represents the first reported cloning of an avian matrix metalloproteinase. The increased expression of the chicken progelatinase by RSV transformation and the tumour promoter PMA suggests that the progelatinase is regulated differently in chicken cells.

A novel transforming growth factor-beta 1 responsive cytoplasmic trans-acting factor binds selectively to the 3'-untranslated region of mammalian ribonucleotide reductase R2 mRNA: role in message stability

Ribonucleotide reductase is a highly regulated enzyme that provides the four deoxyribonucleotides required for DNA synthesis. Our studies showed that TGF-beta 1 treatment of BALB/c 3T3 mouse fibroblasts markedly elevated ribonucleotide reductase R2 mRNA levels, and also increased the half-life of R2 message by 4-fold from 1.5 h in untreated cells to 6 h in treated cells. We describe a novel 75 Kd sequence-specific cytoplasmic factor (p75) that binds selectively to a 83-nucleotide 3'-untranslated region of R2 mRNA and did not bind to the 5'UTR, the coding region of the R2 message or to the 3'UTRs of other mRNAs (from c-myc, GM-CSF and the iron responsive element from the transferrin receptor mRNA), or to the homopolymer poly(A) sequence. p75-RNA binding activity, which requires new protein synthesis, is not present in untreated cells, but is induced following TGF-beta 1 stimulation. The in vivo kinetics of appearance of p75 binding activity paralleled the accumulation of R2 mRNA. Insertion of the 3'-untranslated region into the chloramphenicol acetyltransferase (CAT) message confers TGF-beta 1 induced stability of RNA in stably transfected cells, while the same insert carrying a deletion of the 83-nucleotide fragment had little affect on RNA levels. Furthermore, in vitro decay reactions that contained the 83-nucleotide RNA or deletion of this fragment caused a significant decrease in TGF-beta 1 stabilization of R2 message. A model is presented of R2 message regulation in which TGF-beta 1 mediated stabilization of R2 message involves a specific interaction of a p75-trans-acting factor with a cis-element(s) stability determinant within the 83-nucleotide sequence which is linked to a reduction in the rate of R2 mRNA degradation.

Proliferative activation of quiescent Rat-1A cells by delta FosB

Fos and Jun transcription factors are induced during the normal course of the proliferative response of quiescent cells to serum or to growth factors. We have shown that delta FosB, an alternatively spliced form of FosB, is formed as rapidly as FosB in serum-stimulated Rat-1A cells. Although delta FosB lacks the C-terminal region of FosB carrying the transactivation function, constitutive expression of delta FosB transforms Rat-1A cells as does expression of FosB. The transforming ability of delta FosB suggests that delta FosB may lead to proliferative activation of quiescent cells without activating AP-1-responsive genes. To address this question, FosB or delta FosB was expressed as a fusion protein with the ligand binding domain of the human estrogen receptor (ER) in Rat-1A cells. After estrogen treatment, the fusion protein accumulates in nuclei and forms stable complexes with Jun proteins. We have shown that ER-delta FosB or to a lesser extent ER-FosB triggers quiescent Rat-1A cells to transit G1, initiate DNA replication, and ultimately undergo cell division at least once. Since ER-FosB, but not ER-delta FosB, induced expression of the AP-1-responsive transin/stromelysin gene, we concluded that the N-terminal region and the DNA binding domain of FosB or delta FosB itself have the potential to regulate cell proliferation and that the transactivation function carried by the C-terminal region of FosB is not essential for the proliferative activation of quiescent cells.

Cytoskeletal reorganization and TPA differently modify AP-1 to induce the urokinase-type plasminogen activator gene in LLC-PK1 cells

Urokinase-type plasminogen activator (uPA) is an extracellular protease and expressed in various cells that exhibit dynamic changes in cell morphology, suggesting a link between cytoskeletal reorganization (CSR) and uPA expression. CSR can be induced by pharmacological agents, such as by colchicine for microtubule cytoskeleton and by cytochalasin for microfilament cytoskeleton. Using these agents, we previously showed that CSR induced the uPA gene in LLC-PK1 cells independently of the protein kinase C and cAMP-dependent protein kinase. Here we show that the induction of the uPA gene by CSR is mediated by the activation of c-Jun which interacts with an AP-1-like site located 2 kb upstream of the uPA gene. 12-O-tetradecanoylphorbol 13-acetate (TPA) induces the uPA gene through the same elements, but additionally utilizes an adjacent PEA3 element and induces c-fos. Furthermore, CSR induces a greater accumulation and a more pronounced phosphorylation of c-Jun than TPA induction. AP-1 is a positive regulator of growth and oncogenesis, and CSR is an integral part of these processes. Our results provide a view how CSR and AP-1 could be coupled in these processes. We also show that TPA and CSR act synergistically, suggesting a model where an initial activation signal could be amplified by CSR.

Expression of 92-kD type IV collagenase/gelatinase (gelatinase B) in osteoarthritic cartilage and its induction in normal human articular cartilage by interleukin 1

We report here that a 92-kD gelatinolytic metalloproteinase is expressed as protein and mRNA in human osteoarthritic cartilage, but not in normal adult articular cartilage. Western immunoblotting demonstrated that the 92-kD gelatinolytic activity corresponded to 92-kD type IV collagenase/gelatinase (gelatinase B); mRNA for gelatinase B was identified by Northern blotting. Chondrocytes from normal cartilage also exhibited mRNA for 72-kD type IV collagenase/gelatinase (gelatinase A), tissue collagenase, and stromelysin-1, and these mRNAs were increased in osteoarthritic cartilage. Regional analysis of osteoarthritic cartilage samples from four individuals revealed that gelatinase B mRNA was expressed in grossly fibrillated areas; two of four nonfibrillated cartilage samples failed to exhibit the mRNA, but did have increased levels of mRNA for other neutral metalloproteinases. IL-1 alpha treatment of normal human cartilage explants or isolated chondrocytes induced increased levels of gelatinase B and increased mRNA for tissue collagenase and stromelysin-1. Under identical conditions, mRNA levels for gelatinase A were not increased indicating that regulation of this enzyme in human articular chondrocytes is distinct from that of other metalloproteinases. Our data showing expression of gelatinase B in fibrillated cartilage suggest that it is a marker of progressive articular cartilage degradation in osteoarthritis.

Proliferative activation of quiescent Rat-1A cells by delta FosB

Fos and Jun transcription factors are induced during the normal course of the proliferative response of quiescent cells to serum or to growth factors. We have shown that delta FosB, an alternatively spliced form of FosB, is formed as rapidly as FosB in serum-stimulated Rat-1A cells. Although delta FosB lacks the C-terminal region of FosB carrying the transactivation function, constitutive expression of delta FosB transforms Rat-1A cells as does expression of FosB. The transforming ability of delta FosB suggests that delta FosB may lead to proliferative activation of quiescent cells without activating AP-1-responsive genes. To address this question, FosB or delta FosB was expressed as a fusion protein with the ligand binding domain of the human estrogen receptor (ER) in Rat-1A cells. After estrogen treatment, the fusion protein accumulates in nuclei and forms stable complexes with Jun proteins. We have shown that ER-delta FosB or to a lesser extent ER-FosB triggers quiescent Rat-1A cells to transit G1, initiate DNA replication, and ultimately undergo cell division at least once. Since ER-FosB, but not ER-delta FosB, induced expression of the AP-1-responsive transin/stromelysin gene, we concluded that the N-terminal region and the DNA binding domain of FosB or delta FosB itself have the potential to regulate cell proliferation and that the transactivation function carried by the C-terminal region of FosB is not essential for the proliferative activation of quiescent cells.

Transforming growth factor-beta 1 induces alpha-smooth muscle actin expression in granulation tissue myofibroblasts and in quiescent and growing cultured fibroblasts

Granulation tissue fibroblasts (myofibroblasts) develop several ultrastructural and biochemical features of smooth muscle (SM) cells, including the presence of microfilament bundles and the expression of alpha-SM actin, the actin isoform typical of vascular SM cells. Myofibroblasts have been proposed to play a role in wound contraction and in retractile phenomena observed during fibrotic diseases. We show here that the subcutaneous administration of transforming growth factor-beta 1 (TGF beta 1) to rats results in the formation of a granulation tissue in which alpha-SM actin expressing myofibroblasts are particularly abundant. Other cytokines and growth factors, such as platelet-derived growth factor and tumor necrosis factor-alpha, despite their profibrotic activity, do not induce alpha-SM actin in myofibroblasts. In situ hybridization with an alpha-SM actin probe shows a high level of alpha-SM actin mRNA expression in myofibroblasts of TGF beta 1-induced granulation tissue. Moreover, TGF beta 1 induces alpha-SM actin protein and mRNA expression in growing and quiescent cultured fibroblasts and preincubation of culture medium containing whole blood serum with neutralizing antibodies to TGF beta 1 results in a decrease of alpha-SM actin expression by fibroblasts in replicative and non-replicative conditions. These results suggest that TGF beta 1 plays an important role in myofibroblast differentiation during wound healing and fibrocontractive diseases by regulating the expression of alpha-SM actin in these cells.

Molecular cloning and characterization of a cDNA showing negative regulation in v-src-transformed 3Y1 rat fibroblasts

A differential screening procedure was used to isolate genes that are specifically down-regulated in transformed cells. After screening a cDNA library derived from normal rat fibroblast (3Y1) cells, we obtained several independent cDNAs whose mRNA level was substantially lower in 3Y1 cells transformed with Rous sarcoma virus than in untransformed 3Y1 cells. Among them, N03 cDNA has been characterized extensively. N03 mRNA was also absent from v-mos- or simian virus 40-transformed 3Y1 cells but was present in v-Ha-ras-transformed 3Y1 cells. Nucleotide sequence analysis showed that the N03 protein is composed of 178 amino acid residues and does not have any sequence similarities with proteins in the data base. A putative zinc-finger domain is located in the central part of the sequence and a proline-rich domain is in the C-terminal region. N03 mRNA was detected by Northern blot analysis in several tissues, including lung, kidney, intestine, and brain, but not in liver. Genomic Southern blot hybridization revealed that the N03 gene exists as a single copy in the rat genome and that closely related, single-copy genes are also present in chicken and human.

Cell-shape-associated transcriptional activation of the p52(PAI-1) gene in rat kidney cells

The microfilament-disrupting agent cytochalasin D (CD) increased (by 10-22-fold) the synthesis de novo and extracellular matrix deposition of plasminogen-activator inhibitor type-1 [p52(PAI-1)] in normal rat kidney (NRK) cells. Transition from a flat to a round phenotype occurred concomitantly with, and may actually precede, p52(PAI-1) induction; both the morphological and p52(PAI-1) responses were dose-dependent. Augmented synthesis became evident between 4 and 5 h of treatment of NRK cells with 100 microM-CD, correlating with a transition from 25 to more than 60% rounded cells. CD-associated increases in p52(PAI-1) mRNA abundance and protein biosynthesis were maximal between 6 and 8 h of continuous CD exposure, declined by 50% thereafter, but remained elevated (by at least 6-21-fold respectively over control values) for 24 h. Changes in p52(PAI-1) mRNA abundance at this 24 h point reflected an approx. 5-fold increase in p52(PAI-1)-gene transcription. These data confirm previous suggestions, based on actinomycin D-sensitivity of the inductive response [Higgins & Ryan (1992) Biochem. J. 284, 433-439], that CD-mediated increases in p52(PAI-1) expression are at least partly due to transcription-level events. Since CD also augments specific cellular responses to growth factors or cytokines, the potential effectiveness of this inducer was evaluated both in the presence and absence of serum growth factors using quiescent NRK cells [a growth state in which p52(PAI-1) is not expressed] as a model system. Induction of p52(PAI-1) synthesis and matrix deposition in CD-stimulated quiescent NRK cells was as efficient under growth-factor-deficient conditions as when CD was added simultaneously with serum. CD alone is thus a complete inducer of p52(PAI-1) expression in NRK cells, an observation that supports the contention that cell shape is an important regulatory element in p52(PAI-1)-gene control.

Two adjacent AP-1-like binding sites form the electrophile-responsive element of the murine glutathione S-transferase Ya subunit gene

An electrophile-responsive element (EpRE) in the 5' flanking region of the mouse glutathione S-transferase Ya subunit gene was recently found to be responsible for the induction of gene expression by xenobiotics that contain or acquire by metabolism an electrophilic center. We now find that this EpRE is composed of two adjacent 9-base-pair motifs related in sequence to the AP-1 binding site, a transcriptional enhancer originally identified as the phorbol 12-myristate 13-acetate (PMA) response element and known to be regulated by the binding of protein products of c-jun and c-fos genes. Synthetic oligonucleotides representing each of the AP-1-like binding sites of the EpRE and the AP-1 site consensus sequence were prepared and assayed for their enhancer activity and inducibility by tert-butylhydroquinone, beta-naphthoflavone, and PMA. Single AP-1-like sequences showed a lower enhancer activity than an AP-1 consensus sequence and no inducibility. Two adjacent AP-1-like sites were found to act synergistically and to confer inducibility beyond that observed for a single AP-1 consensus sequence. Examination of the PMA-responsive region of a number of genes shows the presence of adjacent AP-1-like sites and indicates that the structure of the EpRE found in the Ya gene may occur more generally and may be important in regulating the magnitude of the electrophilic response. The present study demonstrates the binding and transactivation of the EpRE by Jun and Fos and indicates that the AP-1 site is part of the EpRE. The induction by PMA or tert-butylhydroquinone appears to be independent of protein kinase C activity since it is not affected by inhibitors of this enzyme.

NGF-induction of the metalloproteinase-transin/stromelysin in PC12 cells: involvement of multiple protein kinases

In previous work, we found that nerve growth factor (NGF) induced expression of the mRNA transcript encoding the metalloproteinase transin/stromelysin in PC12 cells. Transin was found, moreover, to be a "late" gene product whose expression correlated with neurites extension. In this study, various aspects of the NGF intracellular signaling pathway in PC12 cells are investigated. We show that the protein kinase inhibitor staurosporine, but not various other kinase inhibitors, specifically blocked the NGF induction of transin. Preliminary characterization of this staurosporine-sensitive kinase suggest that it does not correspond to a tyrosine kinase, nor various serine kinases, and that it is involved both at the transcriptional and posttranscriptional levels of transin gene regulation. In contrast to these effects of staurosporine, various activators of protein kinases C and A augmented the NGF induction of transin. Similar effects of these kinase inhibitors and activators were also observed with the expression of various immediate-early genes that have been proposed to mediate the transcriptional effects of NGF, including c-fos and c-jun. These data suggest, therefore, that the NGF induction of transin mRNA expression involves multiple protein kinases acting at a number of postreceptor regulatory steps in the NGF signaling pathway.

Activation of endothelial-leukocyte adhesion molecule 1 (ELAM-1) gene transcription

Leukocyte adherence to endothelium is in part mediated by the transient expression of endothelial-leukocyte adhesion molecule 1 (ELAM-1) on endothelial surfaces stimulated by tumor necrosis factor alpha (TNF), interleukin (IL) 1, or bacterial lipopolysaccharide (LPS). The intracellular factors controlling induction of ELAM-1 mRNA and protein are unknown. In nuclear runoff experiments with cultured human umbilical vein endothelial cells (HUVEC), we demonstrate that transcriptional activation of the ELAM-1 gene occurs following stimulation with TNF. Sequence analysis of the 5' flanking region of the ELAM-1 gene reveals consensus DNA-binding sequences for two known transcription factors, NF-kappa B and AP-1. Gel mobility shift assays demonstrate that TNF, IL-1, or LPS (but not IL-2, IL-4, IL-6, interferon gamma, histamine, or transforming growth factor beta) induces activation of NF-kappa B-like DNA binding activity in HUVEC. In contrast, neither TNF, IL-1, nor LPS activates proteins that bind to an AP-1 consensus sequence under these experimental conditions. Phorbol 12-myristate 13-acetate, a known activator of protein kinase C (PKC), weakly induces NF-kappa B-like activity, ELAM-1 mRNA, and ELAM-1 surface expression in HUVEC. However, TNF, IL-1, and LPS do not activate PKC in HUVEC at doses that strongly induce NF-kappa B-like protein activation and ELAM-1 gene expression. PKC blockade with H7 does not inhibit activation of these NF-kappa B-like proteins but does inhibit ELAM-1 gene transcription. We conclude that PKC-independent activation of NF-kappa B in HUVEC with TNF, IL-1, or LPS is associated with, but not sufficient for, activation of ELAM-1 gene transcription.

Characterization of the decay-accelerating factor gene promoter region

Decay-accelerating factor (DAF) expression modulates susceptibility of cells to autologous complement attack. To characterize the regulatory region controlling DAF gene transcription, genomic DNA extending from 815 base pairs (bp) upstream to approximately 4 kilobases downstream of DAF's AUG codon (designated +1) was cloned and sequenced. The 5' flanking sequence showed 59-76% G + C content (-355 to +1), at least one GC box(es) (-135 to -131), and variable length sequences (from -629 to -285) conforming to the motifs TCCTCC and TCn. Nuclease S1 digestions and primer extensions localized a major transcriptional start site to -82/-81, 38 bp downstream of a possible TATA variant, (A)TTTAA. In COS cell transfections, the sequence encompassing -815 to -67 functioned 2.5% as efficiently as the Rous sarcoma virus 3' long terminal repeat, but following deletion upstream of -355 its activity increased approximately 4-fold. Two octanucleotides exhibiting partial homology to phorbol 12-myristate 13-acetate (PMA) and cAMP responsive elements (PREs and CREs, respectively) were detected, and the respective modulators enhanced transcriptional efficiency 2- and approximately 10-fold, respectively. Thus, the DAF gene promoter (i) exhibits sequences resembling both conventional and unconventional transcriptional control elements, (ii) possesses a region with negative regulatory activity, and (iii) responds to PMA and cAMP induction presumably via PRE- and CRE-like enhancer elements.

Cytosolic-nuclear tumor promoter-specific binding protein: association with the 90 kDa heat shock protein and translocation into nuclei by treatment with 12-O-tetradecanoylphorbol 13-acetate

Suspension-cultured HeLa cells possess a cytosolic-nuclear tumor promoter-specific binding protein (CN-TPBP) which lacks protein kinase C activity. This CN-TPBP existed in cytosol of HeLa cells, but translocated into nuclear fraction of the cells after treatment of the cells with 12-O-tetradecanoylphorbol 13-acetate (TPA). The translocation of CN-TPBP induced by TPA became apparent within 10 min after the treatment with TPA, and was completed within 3 h. CN-TPBP bound TPA with the association constant of 1.4 x 10(10) M-1, and also bound teleocidin B, debromoaplysiatoxin, and thapsigargin in a mutually competitive manner. The binding affinity order of synthetic analogs of teleocidin B correlated with the adhesion-inducing potency order of the compounds toward human leukemia cell line HL-60. The apparent molecular weight of CN-TPBP under non-denaturing conditions was estimated to be 66-68 kDa. CN-TPBP forms a complex with the 90 kDa heat shock protein, and the complex was stabilized by the presence of molybdate. These characteristics of CN-TPBP are similar to those of the nuclear receptors of glucocorticoid and dioxin. These findings suggested that CN-TPBP acts as a nuclear receptor for tumor promoters, and that tumor promoters may exert their biological effects by binding to CN-TPBP.

A GC-rich element confers epidermal growth factor responsiveness to transcription from the gastrin promoter

Epidermal growth factor (EGF) and transforming growth factor alpha are important determinants of mucosal integrity in the gastrointestinal tract, and they act both directly and indirectly to prevent ulceration in the stomach. Consistent with this physiological role, EGF stimulates transcription of gastrin, a peptide hormone which regulates gastric acid secretion and mucosal growth. EGF stimulation of gastrin transcription is mediated by a GC-rich gastrin EGF response element (gERE) (GGGGCGGGGTGGGGGG) which lies between -54 and -68 in the human gastrin promoter. The gERE sequence also confers weaker responsiveness to phorbol ester stimulation. The gERE sequence differs from previously described EGF response elements. The gERE DNA sequence specifically interacts with a GH4 DNA-binding protein distinct from previously described transcription factors (Egr-1 and AP2) which bind GC-rich sequences and mediate transcriptional activation by growth factors. Furthermore, the gERE element does not bind the Sp1 transcription factor even though the gERE sequence contains a high-affinity Sp1-binding site (GGCGGG).

Transcription of a subset of human class II major histocompatibility complex genes is regulated by a nucleoprotein complex that contains c-fos or an antigenically related protein

Transcriptional regulation of the human major histocompatibility complex class II genes requires at least two upstream elements, the X and Y boxes, located in the -50- to -150-base-pair region of all class II promoters. The DRA and DPB promoters contain phorbol ester-responsive elements overlapping the 3' side of their X boxes. Mutation of this sequence down-regulates the efficiency of the DRA promoter, suggesting that a positive regulator(s) binds to this site. In this report, anti-sense c-fos RNA and an anti-c-fos antibody were used to show that the product of the protooncogene c-fos or an antigenically related protein is a component of a complex that binds to the X box and is required for maximal transcription from the DRA and DPB promoters. As c-fos (or its related proteins) cannot bind alone to DNA, these results suggest that it may dimerize with other members of the JUN/AP-1 family, such as hXBP1, to participate in the activation of a subset of class II major histocompatibility complex genes.

A GC-rich element confers epidermal growth factor responsiveness to transcription from the gastrin promoter

Epidermal growth factor (EGF) and transforming growth factor alpha are important determinants of mucosal integrity in the gastrointestinal tract, and they act both directly and indirectly to prevent ulceration in the stomach. Consistent with this physiological role, EGF stimulates transcription of gastrin, a peptide hormone which regulates gastric acid secretion and mucosal growth. EGF stimulation of gastrin transcription is mediated by a GC-rich gastrin EGF response element (gERE) (GGGGCGGGGTGGGGGG) which lies between -54 and -68 in the human gastrin promoter. The gERE sequence also confers weaker responsiveness to phorbol ester stimulation. The gERE sequence differs from previously described EGF response elements. The gERE DNA sequence specifically interacts with a GH4 DNA-binding protein distinct from previously described transcription factors (Egr-1 and AP2) which bind GC-rich sequences and mediate transcriptional activation by growth factors. Furthermore, the gERE element does not bind the Sp1 transcription factor even though the gERE sequence contains a high-affinity Sp1-binding site (GGCGGG).

Interleukin-1 or phorbol induction of the stromelysin promoter requires an element that cooperates with AP-1

Interleukin-1, a mediator of inflammation, or tumor promoting phorbol esters induce transcription of stromelysin, a metalloproteinase that degrades extracellular matrix molecules and that is overexpressed in diseases such as rheumatoid arthritis. Sequences required for induction of transcription of the human stromelysin promoter are contained on a 46 base pair fragment. This fragment contains a sequence with a high degree of similarity to the binding site for the transcription factor activator protein-1 (AP-1) and indeed, the AP-1 sequence of this fragment is necessary but not sufficient for the maximal response to phorbol 12-myristate 13-acetate (phorbol) or interleukin-1. Maximal induction requires functional cooperation between the AP-1 sequence and a neighboring upstream regulatory sequence (URS) of the stromelysin promoter which is also necessary but not sufficient. We demonstrate that both the AP-1 sequence and the URS bind phorbol or interleukin-1 induced nuclear proteins. Cooperation of the AP-1 sequence with another sequence present in the stromelysin promoter may be a general mechanism whereby the AP-1 element, which is found in many promoters, achieves a maximal and specific response to various stimuli.

Interleukin-1 beta prevents the stimulatory effect of transforming growth factor-beta on collagen gene expression in human skin fibroblasts

Transforming growth factors beta 1 and beta 2 (TGF-beta 1 and TGF-beta 2) are well-characterized strong inducers of collagen gene expression. A 100 pM concentration of TGF-beta 1 or TGF-beta 2 increases pro alpha 1(I) collagen mRNA levels in human skin fibroblasts 6.6-fold and 7.0-fold respectively, and also increases the accumulation of procollagens in the cell culture medium. Interleukin-1 beta (IL-1 beta) is an inflammatory mediator which also regulates connective tissue metabolism. A small concentration of IL-1 beta (0.01-1.0 unit/ml) slightly increases pro alpha 1(I) collagen mRNA levels (2.2-fold). Here we provide evidence that IL-1 beta prevents the stimulatory effect of TGFs-beta on collagen synthesis in human skin fibroblasts. An IL-1 beta concentration of 1 unit/ml is enough to keep pro alpha 1(I) collagen mRNA levels at control values in cells stimulated by 100 pM-TGF-beta 1. Thus the results indicate that IL-1 beta inhibits collagen synthesis in cells activated by TGFs-beta, whereas it does not significantly change or might even stimulate collagen gene expression in non-activated cells.

Related fibroblast growth factor receptor genes exist in the human genome

We have isolated, from a human tumor cDNA library, a gene encoding a putative receptor-like protein-tyrosine kinase that we call TK14. The amino acid sequence of the TK14 protein is closely related to the available partial sequence of the mouse protein bek, and more distantly related to the sequences of a chicken basic fibroblast growth factor receptor (73% sequence homology) and the apparent human equivalent of this receptor, the FLG protein (encoded by the fms-like tyrosine kinase gene). Overexpression of the TK14 protein by transfection of COS-1 cells with the corresponding cDNA in a simian virus 40-based expression vector leads to the appearance of new cell-surface binding sites for both acidic and basic fibroblast growth factors. This has been demonstrated by specific binding assays and chemical cross-linking experiments using 125I-labeled growth factors. It appears, therefore, that the human genome contains at least two distinct genes, for TK14 and FLG, that code for related fibroblast growth factor receptors.

Epidermal growth factor stimulation of stromelysin mRNA in rat fibroblasts requires induction of proto-oncogenes c-fos and c-jun and activation of protein kinase C

Stromelysin (transin) is a secreted metalloprotease that is transcriptionally induced by a variety of growth factors and oncogenes. We examined the necessity of specific secondary (protein kinase C) and tertiary (c-fos and c-jun protein products) messengers in the transactivation of stromelysin gene expression by epidermal growth factor (EGF). Rat-1 fibroblasts exposed to antisense c-fos DNA or RNA demonstrated that c-fos expression was necessary for complete EGF induction of stromelysin expression. Similar results demonstrating the necessity of c-jun protein in the EGF induction of stromelysin were obtained. We also demonstrated that protein kinase C activation is required for the EGF induction of stromelysin, since phorbol ester desensitization of C kinase proteins abolished the ability of EGF to induce stromelysin mRNA, protein, and promoter activity. In reconstitution experiments, neither c-fos, c-jun, nor C kinase activation alone induced significant stromelysin expression. Overexpression of c-fos and c-jun was able to induce stromelysin to a level similar to that of the growth factor, and stimulation of protein kinase C activity augmented this induction. The data suggest that the EGF induction of stromelysin in rat fibroblasts procedes through a pathway involving c-fos, c-jun, and protein kinase C.

Epidermal growth factor stimulation of stromelysin mRNA in rat fibroblasts requires induction of proto-oncogenes c-fos and c-jun and activation of protein kinase C

Stromelysin (transin) is a secreted metalloprotease that is transcriptionally induced by a variety of growth factors and oncogenes. We examined the necessity of specific secondary (protein kinase C) and tertiary (c-fos and c-jun protein products) messengers in the transactivation of stromelysin gene expression by epidermal growth factor (EGF). Rat-1 fibroblasts exposed to antisense c-fos DNA or RNA demonstrated that c-fos expression was necessary for complete EGF induction of stromelysin expression. Similar results demonstrating the necessity of c-jun protein in the EGF induction of stromelysin were obtained. We also demonstrated that protein kinase C activation is required for the EGF induction of stromelysin, since phorbol ester desensitization of C kinase proteins abolished the ability of EGF to induce stromelysin mRNA, protein, and promoter activity. In reconstitution experiments, neither c-fos, c-jun, nor C kinase activation alone induced significant stromelysin expression. Overexpression of c-fos and c-jun was able to induce stromelysin to a level similar to that of the growth factor, and stimulation of protein kinase C activity augmented this induction. The data suggest that the EGF induction of stromelysin in rat fibroblasts procedes through a pathway involving c-fos, c-jun, and protein kinase C.

Induction of growth factor-receptor and metalloproteinase genes by epidermal growth factor and/or transforming growth factor-alpha in human gastric carcinoma cell line MKN-28

We examined the effects of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) on EGF receptor (EGFR) phosphorylation and the expression of mRNAs for oncogenes, growth factors, their receptors and metalloproteinase genes by MKN-28 gastric carcinoma cells which express EGF, TGF-alpha and EGFR genes. Both EGF and TGF-alpha stimulated EGFR phosphorylation, EGF and TGF-alpha induced FOS, MYC and ERBB-2 oncogene expression. Interestingly, EGF increased the expression of mRNAs for TGF-alpha and EGFR. On the other hand, TGF-alpha increased TGF-alpha mRNA but decreased the expression of mRNAs for EGFR and TGF-beta. Furthermore, mRNAs for interstitial collagenase, stromelysin and procollagen type I genes were also enhanced after treatment with EGF and TGF-alpha. These results indicate that EGF and TGF-alpha successively evoke cascade phenomena which favor tumor progression, invasion and extracellular matrix formation, acting as autocrine growth regulators for gastric carcinomas.

Isolation and characterization of eight tumor necrosis factor-induced gene sequences from human fibroblasts

A lambda cDNA library was prepared from polyadenylated RNA isolated from quiescent human diploid FS-4 fibroblasts stimulated with tumor necrosis factor for 3 h. Differential screening was used to isolate cDNA sequences that are stimulated by tumor necrosis factor. Eight distinct tumor necrosis factor-stimulated gene sequences (designated TSG-1, -6, -8, -12, -14, -21, -27, and -37) were partially sequenced and compared with known sequences from GenBank. TSG-1 was identical to the gene for interleukin-8. TSG-8 corresponded to the gene for monocyte chemotactic and activating factor. TSG-21 and -27 were identical to the genes for collagenase and stromelysin, respectively. The other four sequences showed no homologies with known genes. Patterns of induction of mRNAs corresponding to the eight cloned cDNAs by various cytokines, growth factors, and activators of second messenger pathways were analyzed in FS-4 cells.

Isolation and characterization of eight tumor necrosis factor-induced gene sequences from human fibroblasts

A lambda cDNA library was prepared from polyadenylated RNA isolated from quiescent human diploid FS-4 fibroblasts stimulated with tumor necrosis factor for 3 h. Differential screening was used to isolate cDNA sequences that are stimulated by tumor necrosis factor. Eight distinct tumor necrosis factor-stimulated gene sequences (designated TSG-1, -6, -8, -12, -14, -21, -27, and -37) were partially sequenced and compared with known sequences from GenBank. TSG-1 was identical to the gene for interleukin-8. TSG-8 corresponded to the gene for monocyte chemotactic and activating factor. TSG-21 and -27 were identical to the genes for collagenase and stromelysin, respectively. The other four sequences showed no homologies with known genes. Patterns of induction of mRNAs corresponding to the eight cloned cDNAs by various cytokines, growth factors, and activators of second messenger pathways were analyzed in FS-4 cells.

Induction of a mitogen-responsive gene after expression of the Ha-ras oncogene in NIH 3T3 fibroblasts

A cDNA clone, T1, has been isolated whose corresponding mRNA was transiently expressed at highly elevated levels after conditional expression of the Ha-ras(EJ) gene and after mitogenic activation of quiescent NIH 3T3 cells. Glucocorticoid hormone stimulated substantial T1 expression as well but only in proliferating cells. At least two different signaling pathways participate in the regulation of the T1 gene: a protein kinase C-dependent signal is involved in the response of proliferating NIH 3T3 cells to glucocorticoid in the absence but not the presence of p21ras, whereas a protein kinase C-independent mechanism mediates the response to serum factors. Treatment of cells with the protein kinase inhibitor 2-aminopurine blocked induction of expression of the T1 gene. T1 mRNA accumulation is regulated at the transcriptional level.

Multiple modes of activation of latent human fibroblast collagenase: evidence for the role of a Cys73 active-site zinc complex in latency and a "cysteine switch" mechanism for activation

Latent human fibroblast collagenase (HFC) can be activated by a variety of seemingly disparate means. In addition to the well-characterized activation by trypsin and organomercurial compounds, the enzyme can be activated to various extents by surfactants such as sodium dodecyl sulfate, by chaotropic ions such as SCN-, by disulfide compounds such as oxidized glutathione, by sulfhydryl alkylating agents such as N-ethylmaleimide, and by oxidants such as NaOCl. The underlying basis for these activations is the modification, exposure, or proteolytic release of the Cys73 residue from its habitat in the latent enzyme where it is thought to be complexed to the active-site zinc atom. This residue is not accessible for reaction with small molar excesses of dithionitrobenzoate in native, latent HFC. However, on addition of EDTA, this residue becomes fully exposed and is quantitatively labeled. All modes of activation of latent HFC are believed to involve the dissociation of Cys73 from the active-site zinc atom and its replacement by water, with the concomitant exposure of the active site. This is thought to be the primary event that precedes the well-known autolytic cleavages that are observed following the appearance of collagenase activity. The dissociation of Cys73 from the zinc atom in the latent enzyme "switches" the role of the zinc from a noncatalytic to a catalytic one. This "cysteine switch" mechanism of regulation may be applicable to the entire collagenase gene family.

Transforming growth factor-ßs as modulators of pericellular proteolytic events

Since the discovery of transforming growth factor-ß:s an increasing number of different biological effects have been attributed to this group of proteins. Analysis of the cellular responses to TGFß stimulation at the molecular level has indicated that TGFß acts as an activator of transcription of several genes. This may in part explain the plethora of various functions that have been ascribed to TGFß. In addition to the TGFß family of polypeptides there is an increasing number of related factors, whose major roles appear to be involved in developmental processes. A distinct feature of TGFß is its ability to regulate pericellular proteolysis of cultured cells. As yet this property has not been associated with other members of this group of polypeptides. Depending on the target cell type TGFß may either increase or decrease pericellular proteolytic activity. Proteolytic activation of latent TGFß and its possible inhibition by TGFß-induced protease inhibitors could be a physiological feed-back mechanism in the control of proteolytic activity in the vicinity of cells.

Transin/stromelysin expression in the synovium of rats with experimental erosive arthritis. In situ localization and kinetics of expression of the transformation-associated metalloproteinase in euthymic and athymic Lewis rats

Transin is a neutral metalloproteinase initially isolated from malignantly transformed rat fibroblasts and subsequently shown to be homologous to human stromelysin. We performed Northern blot analysis on synovial tissue specimens from Lewis rats with proliferative and invasive streptococcal cell wall (SCW) arthritis. Transin mRNA was present in abundance, as was the mRNA of the c-myc oncogene, which is associated with cellular proliferation. Immunohistochemical staining of synovia from rats with chronic SCW arthritis showed high-level transin expression in the cells of the lining layer and underlying stroma, as well as in chondrocytes and osteoclasts in subchondral bone. Intense nuclear staining for the Myc oncoprotein was also detected with a cross-reactive antibody to v-Myc. Transin stained similarly in the early, rapid-onset, thymus-independent, acute phase of SCW arthritis. In the T cell-dependent adjuvant arthritis, transin expression was noted by day 4, 6 d before the influx of mononuclear cells and the onset of clinical disease. Athymic rats did not express transin. We concluded that transin is a marker of proliferative, invasive arthritis in rats and appears early in the course of disease development, but requires a competent immune system to sustain its expression in these model arthropathies.

Induction of a mitogen-responsive gene after expression of the Ha-ras oncogene in NIH 3T3 fibroblasts

A cDNA clone, T1, has been isolated whose corresponding mRNA was transiently expressed at highly elevated levels after conditional expression of the Ha-ras(EJ) gene and after mitogenic activation of quiescent NIH 3T3 cells. Glucocorticoid hormone stimulated substantial T1 expression as well but only in proliferating cells. At least two different signaling pathways participate in the regulation of the T1 gene: a protein kinase C-dependent signal is involved in the response of proliferating NIH 3T3 cells to glucocorticoid in the absence but not the presence of p21ras, whereas a protein kinase C-independent mechanism mediates the response to serum factors. Treatment of cells with the protein kinase inhibitor 2-aminopurine blocked induction of expression of the T1 gene. T1 mRNA accumulation is regulated at the transcriptional level.

Fragments of human fibroblast collagenase. Purification and characterization

On purification, human fibroblast collagenase breaks down into two major forms (Mr22,000 and Mr 27,000) and one minor form (Mr 25,000). The most likely mechanism is autolysis, although the presence of contaminating enzymes cannot be excluded. From N-terminal sequencing studies, the 22,000-Mr fragment contains the active site; differential binding to concanavalin A shows the 25,000-Mr fragment is a glycosylated form of the 22,000-Mr fragment. These low-Mr forms can be separated by Zn2+-chelate chromatography. An activity profile of this column, combined with data from substrate gels, indicates no activity against collagen in the 22,000-Mr and 25,000-Mr forms, but rather, activity casein and gelatin. The 27,000-Mr form has no activity. The 22,000/25,000-Mr form can act as an activator for collagenase in a similar way to that reported for stromelysin. The activity of the 22,000/25,000-Mr form is not inhibited by the tissue inhibitor of metalloproteinases (TIMP). The 27,000-Mr C-terminal part of the collagenase molecule therefore appears to be important in maintaining the substrate-specificity of the enzyme, and also plays a role in the binding of TIMP.

Gene regulation by tyrosine kinases: src protein activates various promoters, including c-fos

A promoter of the nuclear proto-oncogene fos was activated by cotransfection with the viral src gene. Ability to transactivate the c-fos promoter was dependent on tyrosine kinase activity, because (i) src mutants which have reduced tyrosine kinase activity due to mutation of Tyr-416 to Phe showed lower promoter activation, (ii) pp60c-src mutants which have increased tyrosine kinase activity due to mutation of Tyr-527 to Phe also augmented c-fos promoter induction, and (iii) mutation in the ATP-binding site of pp60v-src strongly suppressed c-fos promoter activation. Tyrosine kinase activity alone, however, was not sufficient for promoter activation, because of pp60v-src mutant which lacked its myristylation site and consequently membrane association showed no increased c-fos promoter activation. Both the tyrosine kinase- and membrane-association-defective mutants were also unable to induce transformation. Therefore, phosphorylation of membrane-associated substrates appears to be required for both gene expression and cellular transformation by the src protein. Two regions of the c-fos promoter located between positions -362 and -324 and positions -323 and -294 were responsive to src stimulation. We believe that protein tyrosine phosphorylation represents an important step of signal transduction from the membrane to the nucleus.

Rat gene 33: analysis of its structure, messenger RNA and basal promoter activity

Several overlapping cDNA and genomic DNA clones corresponding to mRNA g33 and gene 33, respectively, were isolated and characterized. The mRNA g33 molecule is 2971 nt in length, exclusive of a poly(A+) tail, and encodes a putative 459 amino acid protein (49,946 daltons). The 13.2 kbp gene consists of four exons, three introns, and has two initiation sites located 27 and 30 bp downstream from a TATA box. Transfection of H4IIE cells with a fusion gene 33 (-1900 to +32)/luciferase construct (pSL330A) gave rise to readily detectable luciferase activity. In addition, primer extension analysis of the gene 33/luciferase mRNA transcribed in these experiments showed that transcription initiates in the gene 33 DNA at two sites consistent with those found in vivo. Analysis of the effect of 5' deletions on basal promoter activity showed that, in relation to the promoter activity of pSL330A, approximately 40% of the activity is lost between -1643 and -1050, another approximately 40% between -550 and -475, and deletion to -55 causes a total loss of detectable luciferase activity.

Enhanced jun gene expression is an early genomic response to transforming growth factor beta stimulation

Transforming growth factor beta (TGF beta) is a multifunctional polypeptide that regulates proliferation, differentiation, and other functions of many cell types. The pathway of TGF beta signal transduction in cells is unknown. We report here that an early effect of TGF beta is an enhancement of the expression of two genes encoding serum- and phorbol ester tumor promoter-regulated transcription factors: the junB gene and the c-jun proto-oncogene, respectively. This stimulation was observed in human lung adenocarcinoma A549 cells which were growth inhibited by TGF beta, AKR-2B mouse embryo fibroblasts which were growth stimulated by TGF beta, and K562 human erythroleukemia cells, which were not appreciably affected in their growth by TGF beta. The increase in jun mRNA occurred with picomolar TGF beta concentrations within 1 h of TGF beta stimulation, reached a peak between 1 and 5 h in different cells, and declined gradually to base-line levels. This mRNA response was followed by a large increase in the biosynthesis of the c-jun protein (AP-1), as shown by metabolic labeling and immunoprecipitation analysis. However, differential and cell type-specific regulation appeared to determine the timing and magnitude of the response of each jun gene in a given cell. In AKR-2B and NIH 3T3 cells, only junB was induced by TGF beta, evidently in a protein synthesis-independent fashion. The junB response to TGF beta was maintained in c-Ha-ras and neu oncogene-transformed cells. Thus, one of the earliest genomic responses to TGF beta may involve nuclear signal transduction and amplification by the junB and c-jun transcription factors in concert with c-fos, which is also induced. The differential activation of the jun genes may explain some of the pleiotropic effects of TGF beta.

Gene regulation by tyrosine kinases: src protein activates various promoters, including c-fos

A promoter of the nuclear proto-oncogene fos was activated by cotransfection with the viral src gene. Ability to transactivate the c-fos promoter was dependent on tyrosine kinase activity, because (i) src mutants which have reduced tyrosine kinase activity due to mutation of Tyr-416 to Phe showed lower promoter activation, (ii) pp60c-src mutants which have increased tyrosine kinase activity due to mutation of Tyr-527 to Phe also augmented c-fos promoter induction, and (iii) mutation in the ATP-binding site of pp60v-src strongly suppressed c-fos promoter activation. Tyrosine kinase activity alone, however, was not sufficient for promoter activation, because of pp60v-src mutant which lacked its myristylation site and consequently membrane association showed no increased c-fos promoter activation. Both the tyrosine kinase- and membrane-association-defective mutants were also unable to induce transformation. Therefore, phosphorylation of membrane-associated substrates appears to be required for both gene expression and cellular transformation by the src protein. Two regions of the c-fos promoter located between positions -362 and -324 and positions -323 and -294 were responsive to src stimulation. We believe that protein tyrosine phosphorylation represents an important step of signal transduction from the membrane to the nucleus.

Increases in levels of procollagenase messenger RNA in cultured fibroblasts induced by human recombinant interleukin 1 beta or serum follow c-jun expression and are dependent on new protein synthesis

The protein encoded by the protooncogene c-jun, included in the activator protein-1 (AP-1) complex, is probably the critical trans-acting factor controlling transcription of the procollagenase gene which is rate limiting for subsequent synthesis of procollagenase. Therefore, to elucidate possible mechanisms whereby IL-1 stimulates procollagenase synthesis, we measured levels of c-jun and procollagenase mRNA in human serum-starved dermal fibroblasts in response to human recombinant IL-1 beta (hrIL-1 beta). hrIL-1 beta or serum induced rapid increases in c-jun mRNA levels; mRNA levels declined rapidly after hrIL-1 beta and more slowly after exposure to serum. The increases in levels of c-jun mRNA preceded the increases in procollagenase mRNA. Whereas the increases in levels of procollagenase mRNA were blunted by cycloheximide, those of c-jun mRNA were enhanced. We interpret these results as follows: IL-1 or serum induce transcription of c-jun by mechanisms independent of new protein synthesis; c-JUN, the protein product of c-jun in the AP-1 complex, is an essential mediator of the effects of IL-1 or serum in the subsequent induction of expression of the procollagenase gene.

Enhanced jun gene expression is an early genomic response to transforming growth factor beta stimulation

Transforming growth factor beta (TGF beta) is a multifunctional polypeptide that regulates proliferation, differentiation, and other functions of many cell types. The pathway of TGF beta signal transduction in cells is unknown. We report here that an early effect of TGF beta is an enhancement of the expression of two genes encoding serum- and phorbol ester tumor promoter-regulated transcription factors: the junB gene and the c-jun proto-oncogene, respectively. This stimulation was observed in human lung adenocarcinoma A549 cells which were growth inhibited by TGF beta, AKR-2B mouse embryo fibroblasts which were growth stimulated by TGF beta, and K562 human erythroleukemia cells, which were not appreciably affected in their growth by TGF beta. The increase in jun mRNA occurred with picomolar TGF beta concentrations within 1 h of TGF beta stimulation, reached a peak between 1 and 5 h in different cells, and declined gradually to base-line levels. This mRNA response was followed by a large increase in the biosynthesis of the c-jun protein (AP-1), as shown by metabolic labeling and immunoprecipitation analysis. However, differential and cell type-specific regulation appeared to determine the timing and magnitude of the response of each jun gene in a given cell. In AKR-2B and NIH 3T3 cells, only junB was induced by TGF beta, evidently in a protein synthesis-independent fashion. The junB response to TGF beta was maintained in c-Ha-ras and neu oncogene-transformed cells. Thus, one of the earliest genomic responses to TGF beta may involve nuclear signal transduction and amplification by the junB and c-jun transcription factors in concert with c-fos, which is also induced. The differential activation of the jun genes may explain some of the pleiotropic effects of TGF beta.

AP-1/jun binding sites mediate serum inducibility of the human vimentin promoter

The vimentin gene is inducible by serum in quiescent Balb/c 3T3 cells, but the molecular mechanism of this induction is unknown. The results presented here represent a first step towards the elucidation of the pathway of events leading from growth factor-receptor interaction to this induction. A series of Bal 31 deletions of the human vimentin promoter are used to show that a sequence residing at -700 is responsible for the serum, and also TPA inducibility of this gene. This sequence is able to confer serum inducibility upon uninducible constructs regardless of its position and orientation, indicating that it is this element alone which is required for this induction. The isolated sequence is a strong enhancer as well. Further deletions and the use of synthetic oligonucleotides demonstrate that a 24-mer containing two AP-1/jun binding sites confer both serum and TPA inducibility upon the human vimentin gene. Gel retardation analysis confirms that this sequence binds an AP-1 -like protein.

Modulation of hnRNP A1 protein gene expression by epidermal growth factor in Rat-1 cells

The levels of mRNA encoding hnRNP core protein A1 have been compared in quiescent and proliferating Rat-1 embryonic fibroblasts. Northern blot hybridization analyses using probes made from an A1 cDNA clone, lambda HDP-182, isolated by Cobianchi et al. (J. Biol. Chem. 261:3536-2543 (1986] indicated that three sizes of poly A + RNAs, 1.6, 2.0, & 4.0 kb, have extensive sequence homology. The levels of all three A1 RNA species are responsive to the proliferation state of the cells. Stimulation of quiescent Rat-1 cells with serum or epidermal growth factor resulted in a 2- to 5-fold increase in the levels of each of these three RNAs that was evident after 2 hours and reached a peak after about 8 hours. Addition of the protein synthesis inhibitor, cycloheximide, along with epidermal growth factor completely blocked the upsurge in A1 RNA levels. Thus, the A1 RNA species are not primary transcriptional targets of epidermal growth factor but do show an induction pattern similar to mRNAs encoding some glycolytic enzymes.

Similar effects of adenovirus E1A and glucocorticoid hormones on the expression of the metalloprotease stromelysin

The stromelysin (sml) gene encodes a secreted protease which degrades components of the extracellular matrix. Transformation of NRK49F cells by the E1A region of adenovirus (Ad) type 5 or 12 reduces sml RNA levels, whereas various growth factors or EJras-mediated transformation stimulate sml gene expression in these cells. Nuclear run-on experiments show that AdE1A, growth factors and EJras act on sml gene expression at the level of transcription. Although the sml gene is strongly suppressed in AdE1A-transformed cells, treatment with growth factors or transfection of EJras still causes a raise in sml mRNA levels, indicating that E1A does not block the induction mechanism itself. The effect of glucocorticoid hormones on sml gene expression is very similar to that of AdE1A, in that mRNA levels are lowered without affecting the induction phenomenon. This similarity may provide a clue to the mechanism by which AdE1A represses cellular gene activity.