Human chromosomal localization, tissue/tumor expression, and regulatory function of the ets family gene EHF.

Ets factors are members of an ancient multigene family of transcription factors including oncoproteins and possibly tumor suppressors. We previously characterized a novel divergent ets gene, Ehf (ets homologous factor) in mice. Here we report the cDNA sequence, chromosomal location, and tissue/tumor expression patterns of the human EHF gene and the regulatory activity of the EHF protein. EHF maps to 11p12, which is deleted in many prostate, breast, and lung carcinomas and is a hot spot for inherited deletion- or amplification-associated developmental defects. EHF is differentially expressed in normal tissues and carcinomas and between tumor stages and is most highly expressed in the organs known to form carcinomas upon 11p12 deletion. EHF protein represses the ETS-2 induced activity of both stromelysin-1 and collagenase-1 promoters. These data suggest that EHF may contribute to human development and carcinogenesis and is a candidate for the 11p12 tumor suppressor gene.

p300/cAMP-responsive element-binding protein interactions with ets-1 and ets-2 in the transcriptional activation of the human stromelysin promoter.

In this paper we show that transcription factors Ets-1 and Ets-2 recruit transcription adapter proteins p300 and CBP (cAMP-responsive element-binding protein) during the transcriptional activation of the human stromelysin promoter, which contains palindromic Ets-binding sites. Ets-2 and p300/CBP exist as a complex in vivo. Two regions of p300/CBP between amino acids (a.a.) 328 and 596 and a. a. 1678 and 2370 independently can interact with Ets-1 and Ets-2 in vitro and in vivo. Both these regions of p300/CBP bind to the transactivation domain of Ets-2, whereas the C-terminal region binds only to the DNA binding domain of Ets-2. The N- and the C-terminal regions of CBP (a.a. 1-1097 and 1678-2442, respectively) which lack histone acetylation activity independently are capable of coactivating Ets-2. Other Ets family transcription factors failed to cooperate with p300/CBP in stimulating the stromelysin promoter. The LXXLL sequence, reported to be important in receptor-coactivator interactions, does not appear to play a role in the interaction of Ets-2 with p300/CBP. Previous studies have shown that the stimulation of transcriptional activation activity of Ets-2 requires phosphorylation of threonine 72 by the Ras/mitogen-activated protein kinase signaling pathway. We show that mutation of this site does not affect its capacity to bind to and to cooperate with p300/CBP.

A single nucleotide polymorphism in the matrix metalloproteinase-1 promoter creates an Ets binding site and augments transcription.

Matrix metalloproteinases (MMPs) facilitate cellular invasion by degrading the extracellular matrix, and their regulation is partially dependent on transcription. Binding sites for members of the Ets family of transcription factors are present within MMP promoters and are potent positive regulators. We report a single nucleotide polymorphism at -1607 bp in the MMP-1 promoter, where an additional guanine (G) creates an Ets binding site, 5'-GGA-3'. This polymorphism displays significantly higher transcription in normal fibroblasts and in melanoma cells than the 1 G polymorphism, and it binds substantially more nuclear extract and recombinant ETS-1. Analysis of control DNAs from the Center d'Etude du Polymorphisme Humain pedigrees reveals that this polymorphism is not a mutation, with a frequency of the 2 G polymorphism at 30%. In contrast, in eight tumor cell lines, this frequency increased to 62.5% (P < 0.0001). Thus, this MMP-1 polymorphism contributes to increased transcription, and cells expressing the 2 G polymorphism may provide a mechanism for more aggressive matrix degradation, thereby facilitating cancer progression.

The Ets transcription factors interact with each other and with the c-Fos/c-Jun complex via distinct protein domains in a DNA-dependent and -independent manner.

The transcription factors Fos, Jun, and Ets regulate the expression of human stromelysin-1 and collagenase-1 genes. Recently, we found that ERG, an Ets family member, activates collagenase-1 gene but not stromelysin-1 by physically interacting with c-Fos/c-Jun. Interestingly, ERG binds to stromelysin-1 promoter and represses its activation by ETS2. Here, to investigate the molecular mechanism of this regulation, we have used an in vitro protein-protein interaction assay and studied the transcription factor interactions of ETS2. We found that ETS2 could weakly associate with in vitro synthesized ETS1, c-Fos, and c-Jun and strongly with c-Fos/c-Jun complex and ERG via several distinct ETS2 domains including the C-terminal region that contains the DNA-binding domain. Strikingly, these interactions were stabilized in vitro by DNA as they were inhibited by ethidium bromide. Both the N-terminal region, comprising the transactivation domain, and the C-terminal region of ETS2 associated with ERG and, interestingly, the interaction of ERG through the transactivation domain of ETS2 was DNA-independent. The DNA-dependent interaction of ETS2 with c-Fos/c-Jun was enhanced by specific DNA fragments requiring two Ets-binding sites of the stromelysin-1 promoter. Using the two hybrid system, we also demonstrated that ETS2 interacts with c-Jun or ERG in vivo.

Hydrocortisone modulates the expression of c-ets-1 and 72 kDa type IV collagenase in chicken dermis during early feather morphogenesis.

At the onset of chicken feather morphogenesis, dermal cells migrate along bundles of collagen fibers to colonize areas where bud outgrowth takes place. Chicken embryos treated with hydrocortisone during the critical phase of dermal rearrangement show featherless skin areas in which the dermis exhibits an increase of interstitial collagen. We had previously demonstrated that c-ets-1 is a nuclear transcription factor expressed in the dermis at the beginning of feather morphogenesis. Here we study, by in situ mRNA hybridization, the expression of c-ets-1 in the dermis of chicken embryos treated with hydrocortisone. We found that, among the two distinct products (p54 and p68) encoded by the chicken c-ets-1, the expression of the p68 product increased while expression of p54 decreased after hydrocortisone treatment. Since Ets-1 regulates matrix-metalloproteinases genes, we analyzed the expression of the 72 kDa type IV collagenase in both normal and hydrocortisone-treated embryos. We demonstrated that 72 kDa type IV collagenase mRNA expression decreased in the dermis after hydrocortisone treatment and that its expression correlated with that of p54c-ets-1. Taken together, these results indicate that hydrocortisone modulates c-ets-1 expression. In addition, they raise the interesting possibility that c-ets-1 might be involved in an altered pattern of feather development mediated by the accumulation of collagen due to a decrease in collagenase activities.

Erg, an Ets-family member, differentially regulates human collagenase1 (MMP1) and stromelysin1 (MMP3) gene expression by physically interacting with the Fos/Jun complex.

Collagenase1 (MMP1) and stromelysin1 (MMP3) are extracellular proteolytic enzymes that degrade connective tissue macromolecules and basement membranes. Both genes are regulated by the Ets and Fos/Jun families of transcription factors/oncoproteins. Here, we show that two members of the Ets-family, Ets2 and Erg and their combinations differentially regulate collagenase1 and stromelysin1 promoter activity. In transiently transfected cells, Ets2 activates both promoters whereas Erg induces collagenase1 but not stromelysin1 promoter activity. Moreover, Erg completely inhibits stromelysin1 promoter activation by Ets2. In gel shift assays however, the Erg protein bound little or not to the collagenase1 promoter, whereas it bound to the stromelysin1 promoter. By site-specific mutagenesis, we identified one major site at -88 that abolished collagenase1 promoter activation by Erg. Surprisingly, mutation of the collagenase1 AP1 site at -73 also abolished the activation by Erg suggesting that Erg cooperates with Fos/Jun in collagenase1 promoter regulation. Indeed, gel shift and in vitro protein interaction studies showed that Erg binds to the Fos/Jun complex. Thus, Erg represents the first example of a transcription factor that can distinguish between the collagenase1 and stromelysin1 promoters in that when Erg is recruited by Fos/Jun at the promoter, it transcriptionally activates collagenase1 gene but not stromelysin1 expression.

Characterization of the 46-kDa intermediates of matrix metalloproteinase 3 (stromelysin 1) obtained by site-directed mutation of phenylalanine 83.

The precursor of matrix metalloproteinase 3 (MMP-3/ stromelysin 1) is activated in vitro by proteinases or mercurial compounds by stepwise processes which include the initial formation of short-lived intermediates and the subsequent intermolecular cleavage of the His82-Phe83 bond to generate the fully activated mature MMP-3 (Nagase, H., Enghild, J. J., Suzuki, K., and Salvesen, G. (1990) Biochemistry 29, 5783-5789). To study the enzymatic properties of the intermediates we have mutated either His82 or Phe83 to Arg to obtain a stable MMP-3 intermediate. The mutant proteins were expressed in Chinese hamster ovary K-1 cells using a mammalian expression system. The proMMP-3(H82R) mutant was activated by chymotrypsin, elastase, and 4-aminophenylmercuric acetate to the 45-kDa MMP-3 with similar mechanism and kinetics as the wild-type. In contrast, the activation of the proMMP-3(F83R) mutant by proteinases or 4-aminophenylmercuric acetate resulted in 46-kDa forms, which retained 13, 14, or 15 amino acids of the pro-domain depending on the activators. The proteinase-activated MMP-3(F83R) intermediates exhibited little enzymatic activity, but they were partially active after treatment with SH-reacting reagents. These molecules could bind to the tissue inhibitor of metalloproteinases-1 and alpha 2-macroglobulin. However, the SH group of Cys75 of the intermediates was not modified by SH-reagents, indicating that the enzymatic activity generated by SH-reagents resulted from molecular perturbation of the enzyme rather than their interaction with Cys75. When gelatin and transferrin were digested with the 46-kDa intermediates the products were different from those generated by the wild-type MMP-3, suggesting an alteration in substrate specificity. The treatment of proMMP-3 with trypsin resulted in the formation of a 45-kDa MMP-3 with an NH2-terminal Thr85, whose activity and substrate specificity were similar to those of the 46-kDa MMp-3(F83R) obtained from the proMMP-3(F83R) mutant. These observations indicate that the correct processing at the His82-Phe83 bond is critical for expression of the full activity and the specificity of MMP-3.

Promoter elements in the transcriptional activation of the human stromelysin-1 gene by the inflammatory cytokine, interleukin 1.

Stromelysin-1, a tissue-remodelling metalloproteinase synthesized by fibroblasts, has proteolytic activity against a variety of extracellular matrix components. Stromelysin-1 gene transcription is induced by the inflammatory cytokine interleukin (IL)-1. In fibroblasts transiently transfected with constructs containing 5'-deletion mutants of the human stromelysin-1 gene promoter, IL-1-induced transcriptional activity was abolished with the removal of region -102 to -54. This region includes an AP-1 binding site at positions -70 to -64. The AP-1 site alone increased the basal activity of and conferred minimal IL-1 inducibility onto the heterologous gene promoter of thymidine kinase. Interestingly, although the removal of the AP-1 site from the native promoter (-1303 to +4) affected the absolute levels of IL-1-induced and basal promoter activity, it did not alter their ratio, indicating the involvement of regions outside the AP-1 site in the IL-1 response. Of the stromelysin-1 5' flanking sequence examined, only the region -274 to -54 could confer IL-1 inducibility to a heterologous promoter independently of the AP-1 site. This region also bound specific nuclear factors. Further analysis revealed that the region composed of -86 to -71 and -63 to -54 could independently respond to IL-1 and bind protein of whole cell extracts. Protein binding to this region and to the AP-1 site was modestly induced by IL-1 treatment. From these results we conclude that, in fibroblasts, the AP-1 site (-70 to -64) is not necessary for the IL-1 response; however, it probably interacts through protein associations with the responsive region immediately surrounding it in the absolute transcriptional activation of the human stromelysin-1 gene by IL-1.

A polyomavirus enhancer A-binding protein-3 site and Ets-2 protein have a major role in the 12-O-tetradecanoylphorbol-13-acetate response of the human stromelysin gene.

The expression of stromelysin, a major matrix metalloproteinase of connective tissues, is regulated by several cytokines, growth factors, protooncogenes as well as by 12-O-tetradecanoylphorbol-13-acetate (TPA). The human stromelysin gene promoter contains an activator protein-1 (Fos/Jun) binding site at -70, which is required for basal expression but is not necessary for the TPA response. In this study, using promoter deletion mutants in transient gene transfection experiments, we first identify the sequence from -220 to -202 as necessary for the TPA response of the stromelysin gene. Further, among the restriction fragments from the 1.3-kilobase long promoter, only the proximal fragment (-274 to -101) conferred a TPA response on the heterologous thymidine kinase gene promoter. The -220 to -202 sequence contains two copies of a motif similar to the polyomavirus enhancer A-binding protein-3 (PEA-3) site, which binds the Ets family of oncoproteins and transcription factors. Point mutations of either one of the two PEA-3 sites, in the 1.3-kilobase long stromelysin promoter context, reduced basal gene expression. However, only the mutation of the proximal, but not the distal PEA-3 site, significantly inhibited the TPA response. In cotransfection experiments, the Ets-2 protein transactivated the stromelysin promoter and the promoter proximal fragment containing the PEA-3 sites but not the promoters containing mutated PEA-3 sites. These data suggest that the PEA-3 site, but not the activator protein-1 site, and Ets-2 protein have a major role in the TPA induction of the human stromelysin gene transcription.

The AP-1 site is required for basal expression but is not necessary for TPA-response of the human stromelysin gene.

We have studied the activity of the AP-1 site, a target for the Fos and Jun family of transcription factors, in the context of the human stromelysin promoter (-1303 to +4). In transiently transfected human HepG2, HeLa and fibroblast cell cultures, point-mutations in any position of the stromelysin AP-1 sequence TGAGTCA (-70 to -64) reduced both the basal level and TPA-induced expression from the stromelysin promoter. TPA-induction fold of the mutant promoters, however, was comparable to that of the wild-type promoter. Similarly, antisense c-Fos mRNA expression reduced basal activity but had no significant effect on the relative TPA-response of the stromelysin promoter. Further, in mouse F9 cells cotransfected with c-Fos and c-Jun expression plasmids, the transfected wild-type stromelysin promoter activity was increased 57-fold whereas no transactivation was detected for an AP-1 mutant stromelysin promoter. In gelshift assays, stromelysin promoter fragments (-101 to -11), containing the mutated AP-1 site, all failed to bind or compete for the in vitro synthesized Fos and Jun proteins. We interpret these data to suggest that the Fos and Jun proteins, or similar activity, and the AP-1 site are required for the basal level expression of the human stromelysin gene. Strikingly, these data also suggest that the stromelysin AP-1 site is not necessary for the TPA-response.

Evolution of collagen IV genes from a 54-base pair exon: a role for introns in gene evolution.

The exon structure of the collagen IV gene provides a striking example for collagen evolution and the role of introns in gene evolution. Collagen IV, a major component of basement membranes, differs from the fibrillar collagens in that it contains numerous interruptions in the triple helical Gly-X-Y repeat domain. We have characterized all 47 exons in the mouse alpha 2(IV) collagen gene and find two 36-, two 45-, and one 54-bp exons as well as one 99- and three 108-bp exons encoding the Gly-X-Y repeat sequence. All these exons sizes are also found in the fibrillar collagen genes. Strikingly, of the 24 interruption sequences present in the alpha 2-chain of mouse collagen IV, 11 are encoded at the exon/intron borders of the gene, part of one interruption sequence is encoded by an exon of its own, and the remaining interruptions are encoded within the body of exons. In such "fusion exons" the Gly-X-Y encoding domain is also derived from 36-, 45-, or 54-bp sequence elements. These data support the idea that collagen IV genes evolved from a primordial 54-bp coding unit. We furthermore interpret these data to suggest that the interruption sequences in collagen IV may have evolved from introns, presumably by inactivation of splice site signals, following which intronic sequences could have been recruited into exons. We speculated that this mechanism could provide a role for introns in gene evolution in general.

Isolation of a putative collagen-like gene from the sea urchin Paracentrotus lividus.

Using a Caenorhabditis elegans collagen probe we have isolated a 17.6 kb clone from a Paracentrotus lividus genomic library. Sequencing of nearly 2.6 kb identified five open reading frames flanked at both sides by splice site consensus sequences and coding for ninety-five uninterrupted Gly-X-Y repeats. Interestingly, three of the putative exons exhibit sizes which are identical to those featured by vertebrate fibrillar collagen genes, namely 54 bp and 99 bp. Hybridization of the Gly-X-Y encoding sequences to RNA extracted from different developmental stages identified a specific 6 kb transcript, which appears first at mid-gastrula, greatly increases at prism and then progressively accumulates until pluteus stage. Based on these data, we conclude that the genomic clone is likely to code for a developmentally regulated mRNA whose expression coincides with the reported time of appearance of collagenous molecules in the sea urchin embryo.

alpha alpha alpha anti-4.2 Haplotype and heterozygous beta null thalassemia in a Sicilian family.

The presence of the alpha alpha alpha anti-4.2 haplotype and heterozygous beta null thalassemia in a Sicilian family is described. These findings confirm the presence in Italy of a leftward deletion (-alpha 4.2) and indicate that this may not be rare. Furthermore, although the beta thalassemia determinant in this family has a severe expression, the interaction with the triplicated alpha gene does not necessarily express itself as thalassemia intermedia.