Novel upstream elements and the TATA-box region mediate preferential transcription from the uteroglobin promoter in endometrial cells

Elements of the rabbit uteroglobin promoter mediating its transcription in epithelial cells from the endometrium and lung

The rabbit uteroglobin gene is specifically expressed in certain epithelial cells of ontogenetically unrelated origin. In the endometrium, expression is restricted to the glandular and luminal epithelium and is inducible by progesterone and estradiol. In the lung, Clara cells lining the bronchiolar epithelium show constitutive expression of uteroglobin, which is modulated by glucocorticoids. To explore the molecular basis for this cell type specificity, we have transiently transfected the uteroglobin promoter region fused to the chloramphenicol acetyl transferase gene (CAT gene) in the endometrial cell line Ishikawa; in the human lung cell line NCI-H441, which shows morphological Clara cell characteristics; in HeLa cells; and in three fibroblast cell lines. The uteroglobin promoter efficiently drives expression of the CAT gene in Ishikawa and NCI-H441 cells, but not in HeLa and fibroblast cells. To identify the responsible elements we have analyzed progressive promoter 5'-deletion mutants and randomly generated linker scanning mutants spanning the sequence from -258 to -14 of the uteroglobin promoter. Transfection experiments reveal seven mutation-sensitive regions located around -30, -70, -95, -130, -190, -230, and -255. Several mutants display strong cell type-specific phenotypes. Most significantly, the integrity of the region around -190 is essential for full CAT gene expression in Ishikawa cells, but not in NCI-H441 cells.

Uteroglobin: a steroid-inducible immunomodulatory protein that founded the Secretoglobin superfamily

Blastokinin or uteroglobin (UG) is a steroid-inducible, evolutionarily conserved, secreted protein that has been extensively studied from the standpoint of its structure and molecular biology. However, the physiological function(s) of UG still remains elusive. Isolated from the uterus of rabbits during early pregnancy, UG is the founding member of a growing superfamily of proteins called Secretoglobin (Scgb). Numerous studies demonstrated that UG is a multifunctional protein with antiinflammatory/ immunomodulatory properties. It inhibits soluble phospholipase A(2) activity and binds and perhaps sequesters hydrophobic ligands such as progesterone, retinols, polychlorinated biphenyls, phospholipids, and prostaglandins. In addition to its antiinflammatory activities, UG manifests antichemotactic, antiallergic, antitumorigenic, and embryonic growth-stimulatory activities. The tissue-specific expression of the UG gene is regulated by several steroid hormones, although a nonsteroid hormone, prolactin, further augments its expression in the uterus. The mucosal epithelia of virtually all organs that communicate with the external environment express UG, and it is present in the blood, urine, and other body fluids. Although the physiological functions of this protein are still under investigation, a single nucleotide polymorphism in the UG gene appears to be associated with several inflammatory/autoimmune diseases. Investigations with UG-knockout mice revealed that the absence of this protein leads to phenotypes that suggest its critical homeostatic role(s) against oxidative damage, inflammation, autoimmunity, and cancer. Recent studies on UG-binding proteins (receptors) provide further insight into the multifunctional nature of this protein. Based on its antiinflammatory and antiallergic properties, UG is a potential drug target.

Bovine herpesvirus 4 is tropic for bovine endometrial cells and modulates endocrine function

Bovine postpartum uterine disease, metritis, affects about 40% of animals and is widely considered to have a bacterial aetiology. Although the gamma-herpesvirus bovine herpesvirus 4 (BoHV-4) has been isolated from several outbreaks of metritis or abortion, the role of viruses in endometrial pathology and the mechanisms of viral infection of uterine cells are often ignored. The objectives of the present study were to explore the interaction, tropism and outcomes of BoHV-4 challenge of endometrial stromal and epithelial cells. Endometrial stromal and epithelial cells were purified and infected with a recombinant BoHV-4 carrying an enhanced green fluorescent protein (EGFP) expression cassette to monitor the establishment of infection. BoHV-4 efficiently infected both stromal and epithelial cells, causing a strong non-apoptotic cytopathic effect, associated with robust viral replication. The crucial step for the BoHV-4 endometriotropism appeared to be after viral entry as there was enhanced transactivation of the BoHV-4 immediate early 2 gene promoter following transient transfection into the endometrial cells. Infection with BoHV-4 increased cyclooxygenase 2 protein expression and prostaglandin estradiol secretion in endometrial stromal cells, but not epithelial cells. Bovine macrophages are persistently infected with BoHV-4, and co-culture with endometrial stromal cells reactivated BoHV-4 replication in the persistently infected macrophages, suggesting a symbiotic relationship between the cells and virus. In conclusion, the present study provides evidence of cellular and molecular mechanisms, supporting the concept that BoHV-4 is a pathogen associated with uterine disease.

The transcription factor SOX17 is involved in the transcriptional control of the uteroglobin gene in rabbit endometrium

The transcription of the uteroglobin gene (ug) is induced by progesterone in the rabbit endometrium, primarily through the binding of the progesterone receptor to the distal region of the ug promoter. However, other transcription factors participate in the progesterone action. The proximal ug promoter contains several putative consensus sequences for the binding of various progesterone-dependent endometrial nuclear factors (Perez Martinez et al. [1996] Arch Biochem Biophys 333: 12-18), suggesting that several transcription factors might be implicated in the hormonal induction of ug. We report here that one of these progesterone-dependent factors specifically binds to the sequence CACAATG (-183/-177) of the rabbit ug promoter. This sequence (hereafter called element G') is very similar to the consensus sequence for binding of the SOX family of transcription factors. Mutation of the element G' reduced transcription from the ug promoter in transient expression experiments. The endometrial factor was purified and analyzed by nano-liquid chromatography and ion trap coupled mass spectrometry yielding two partial amino acid sequences corresponding to a region of SOX17 that is highly conserved inter-species. This identification was confirmed by immunological techniques using a specific anti-SOX17 antibody. In agreement with the above findings, overexpression of SOX17 in transfected endometrial cells increased transcription from the ug promoter. SOX17 gradually accumulated in the nucleus in vivo concomitant with the induction of ug expression by progesterone in the endometrium. Thus, these findings implicate, for the first time, SOX17 in the transcriptional control of rabbit ug.

Expression of TCF, TPF/YY1, and the Sp family transcription factors in rabbit endometrium throughout pregnancy

BACKGROUND

TCF, TPF/YY1, and the Sp family are specific transcription factors that bind sequences found within the uteroglobin (UG) gene promoter region that are necessary for transcription. To date, UG gene expression and regulation in vivo are not fully understood. The purpose of this study was to assess the expression patterns of these factors in the rabbit endometrium throughout pregnancy.

METHODS

Endometrial nuclear extracts were obtained from female rabbits on days 0, 3, 5, 7, 15, and 28 after mating. Transcription factor expression was assessed by DNA-protein binding assays using endometrial nuclear proteins and specific oligonucleotides. Band shifts were observed on 4% acrylamide gels and analyzed by densitometry.

RESULTS

The expression patterns of the transcription factors analyzed here differed, as TPF/YY1 and Sp3/SpR-2 were expressed constitutively while TCF and Sp1 showed variable expression patterns throughout pregnancy.

CONCLUSIONS

Our results suggest that UG gene expression in the intact pregnant rabbit is controlled by two constitutive and two regulated factors, and that the DNA-binding sites are located at the TATA box and the GT1 sites within the gene promoter.

Two progesterone-dependent endometrial nuclear factors bind to an E-box in the rabbit uteroglobin gene promoter: involvement in tissue-specific transcription

We studied the implications of progesterone-dependent transcription factors in the hormonal and tissue-specific induction of the uteroglobin gene (ug) in the rabbit endometrium. Previously, we have observed the interaction of two progesterone-dependent endometrial nuclear proteins (TRBPs) with sequences downstream from the ug TATA box. Using electrophoretic mobility shift assays (EMSA) we show here that TRBPs specifically interacted with an E-box localized almost immediately downstream from the ug TATA box. UV crosslinking of affinity-purified TRBPs to the radiolabeled oligonucleotide probe confirmed that these factors were proteins with molecular mass of about 40-50 kDa. Ferguson's analysis of the Mr of the DNA-TRBP complexes suggested that TRBPs interacted with the E-box either as homo- or heterodimers. This interaction did not result in detectable bending of the DNA. EMSA analysis with nuclear extracts from different rabbit tissues suggested that TRBPs might be endometrium-specific nuclear factors. Involvement of the E-box in the tissue-specific transcription from the ug promoter was assessed by transient expression experiments using different cell lines transfected with a reporter gene driven by the ug promoter which contained either the intact E-box or a mutated version that completely abolished its interaction with TRBPs. These experiments indicated that, in all cell lines of nonendometrial lineage, destruction of the E-box increased transcription from the ug promoter, whereas in two cell lines of endometrial origin this mutation either had no appreciable effect or slightly reduced the transcription from the promoter. Thus, this E-box and endometrial helix-loop-helix proteins might be involved in the hormonal and tissue-specific regulation of ug transcription.

Hormone-dependent recruitment of NF-Y to the uteroglobin gene enhancer associated with chromatin remodeling in rabbit endometrial epithelium

Expression of the rabbit uteroglobin gene is hormonally induced in cells of the endometrial epithelium during the preimplantation phase of pregnancy. Here we show that progesterone activation of the gene is mediated by two clusters of hormone responsive elements located between 2.4 and 2.7 kilobase pairs upstream of the transcriptional start site. Between these two clusters, genomic footprinting studies in the intact endometrial epithelium reveal the hormone-inducible occupancy of several cis-acting elements. One of the protected elements shows sequence homology to the consensus binding site of the transcription factor NF-Y, which binds to the element in gel shift experiments. This uteroglobin Y box is essential for enhancer activity in transient transfection experiments with endometrial and non-endometrial cell lines, in accordance with the ubiquitous expression of NF-Y. To understand why binding of this ubiquitous factor to the uteroglobin Y box in endometrium depends on hormone induction, we examined the chromatin structure of the relevant gene region. In the uninduced state, the enhancer region appears to be organized into positioned nucleosomes. Upon hormone induction, this nucleosomal pattern is lost and the enhancer region becomes hypersensitive to nucleases, suggesting that a hormone-induced change in the local chromatin structure unmasks previously unaccessible binding sites for transcription factors. Our results emphasize the limitations of using transient transfection assays for the functional analysis of cis-acting elements and underline the need for including the native chromatin organization in this kind of studies.

Gene transfer to cultured human endometrial stromal cells: a model to study cyclooxygenase-2 gene regulation

OBJECTIVE

To compare and optimize conditions for gene transfer to human endometrial stromal cells derived from primary culture and to determine the effect of interleukin-1beta (IL-1beta) and phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator. on the promoter activity of the human cyclooxygenase-2 (COX-2) gene.

DESIGN

Prospective controlled study.

SETTING

Academic research laboratory.

PATIENT(S)

Women undergoing benign gynecologic surgery for indications other than endometrial diseases.

INTERVENTION(S)

Endometrial stromal cells were used for transient transfection study.

MAIN OUTCOME MEASURE(S)

Luciferase activity in transfected endometrial stromal cells.

RESULT(S)

Gene transfer mediated by cationic lipid was more efficient and more consistent. Lipofectamine, a polycationic lipid, yielded the highest efficiency. Phorbol 12-myristate 13-acetate (30 nM) and IL-1beta (100 ng/mL) increased COX-2 promoter activity by 2.6-fold and 2.2-fold, respectively.

CONCLUSION(S)

Induction of COX-2 by IL-1beta and PMA suggests that COX-2 and prostaglandin have important roles in the growth and differentiation of endometrial stromal cells. This model can be used to explore the roles of different promoter regulatory elements in COX-2 gene activation.

Combinatorial action of HNF3 and Sp family transcription factors in the activation of the rabbit uteroglobin/CC10 promoter

It has been reported that respiratory epithelium-specific transcription is mediated by thyroid transcription factor 1 and members of the HNF3/forkhead family of transcription factors. Here, we show that the uteroglobin/Clara cell 10-kDa promoters from rabbit and man are regulated by HNF3alpha and HNF3beta but not by HFH-4 and TTF-1. We have identified two HNF3-responsive elements in the rabbit uteroglobin/CC10 promoter located around 95 and 130 base pairs upstream of the transcriptional start site. Both elements contribute to promoter activity in H441 cells expressing uteroglobin/CC10 and HNF3alpha. Gene transfer experiments into Drosophila Schneider cells that lack many mammalian transcription factor homologs revealed that HNF3alpha and HNF3beta on their own cannot activate the uteroglobin/CC10 promoter. However, HNF3alpha and HNF3beta strongly enhanced Sp1-mediated promoter activation. Synergistic activation by HNF3alpha and Sp1 was absolutely dependent on the integrity of two Sp1 sites located at around -65 and -230. We show further that multiple activation domains of Sp1 are required for cooperativity with HNF3alpha. These studies demonstrate that transcription from the rabbit uteroglobin/CC10 promoter in lung epithelium is controlled by the combinatorial action of the cell-specific factor HNF3alpha and the ubiquitous factor Sp1.

Novel elements in the uteroglobin promoter are a functional target for prolactin signaling

To quantify uteroglobin (UG) gene expression, varying lengths of 5' flanking sequence were subcloned into a luciferase reporter plasmid and introduced into HRE-H9 uterine epithelial cells. In response to estrogen, prolactin (PRL) and progesterone, transcriptional activity was maximal for the full-length construct, pUG3.1-LUC. Transcriptional activity was reduced (P < 0.05) by the removal of the progesterone receptor binding site, tested with pUG2.3-LUC, and eliminated (P < 0.05) by the removal of the remaining 5' flanking sequences, tested with pUG0.1-LUC. When the effects of PRL +/- progesterone were evaluated, progesterone alone increased (P < 0.05) the transcriptional activity of pUG3.1-LUC, and the deletion mutant, pUG3.1deltaRUSH-LUC. Transcription of pUG3.1-LUC was further increased (P < 0.05) by PRL + progesterone. However, deletion of the proximal promoter region -170/-85, tested with pUG3.1deltaRUSH-LUC, eliminated (P > 0.05) the PRL effect. These data support the speculation that RUSH proteins which bind to this region of the promoter play an important regulatory role in PRL signal transduction.

A CACCC box-like cis-regulatory element of the Epstein-Barr virus ED-L2 promoter interacts with a novel transcriptional factor in tissue-specific squamous epithelia

The Epstein-Barr (EBV) virus induces a lytic state after infecting epithelial cells. Subsequently, there is infection of B lymphocytes with two types of cycles, latent and lytic. Apart from linkage of the EBV latent membrane protein-1 (LMP-1) with benign and malignant conditions of squamous epithelial cells, little is known about other EBV gene products that may be important in these processes as well as cellular transcriptional factors that regulate EBV gene expression in these epithelial cells. The EBV ED-L2 promoter, an early lytic cycle promoter, is located upstream of a transcription start site for a short open reading frame designated BNLF2 and just downstream of the BNLF1 (LMP-1) open reading frame. We have previously used the EBV ED-L2 promoter to target oncogenes in transgenic mice, resulting in tissue-specific expression in the tongue, esophagus, forestomach, and skin, all sharing stratifying squamous epithelia, alternatively called keratinocytes. In the present study, we have functionally dissected the ED-L2 promoter by making deletion constructs fused to the luciferase reporter gene with transient transfections into squamous and nonsquamous epithelial cell lines as well as B lymphocytes. A CACCC box-like cis-regulatory element has been identified that is located between -218 and -187 base pairs of the ED-L2 promoter that confers significant promoter activity only in squamous epithelial cells. This cis-regulatory element is active in a heterologous minimal herpes simplex virus thymidine kinase promoter reporter gene construct when transfected into squamous epithelial cells but not in nonsquamous epithelial cells. DNA gel mobility shift assays have led to the identification of DNA-protein complexes that bind the CACCC box-like element. One of these proteins is a novel transcriptional factor that is uniquely active in stratified squamous epithelial cells, designated as keratinocyte specific factor (KSF). KSF may be related to Sp1 but appears to be distinct from Sp1. In addition, KSF may interact with related or identical cis-regulatory elements found in human papillomavirus-11 E6 and cytokeratin K3 promoters that are active in keratinocytes. In aggregate, KSF may be important in the transcriptional regulation of viral and eukaryotic genes in keratinocytes.

Binding of YY1 to a site overlapping a weak TATA box is essential for transcription from the uteroglobin promoter in endometrial cells

The gene for rabbit uteroglobin codes for a small calcium-, steroid-, and biphenyl metabolite-binding homodimeric protein which is expressed in a variety of epithelial cell types such as Clara cells (lung) and the glandular and luminal cells of the endometrium. One important region mediating its efficient transcription in a human endometrium-derived cell line, Ishikawa, is centered around a noncanonical TATA box. Two factors, TATA core factor (TCF), expressed in cell lines derived from uteroglobin-expressing tissues, and the ubiquitously expressed TATA palindrome factor, bind to the DNA major groove at two adjacent sites within this region. Here, we report the identification of the TATA palindrome factor as the transcription/initiation factor YY1 by microsequencing of the biochemically purified factor from HeLa cells. The binding site for YY1 within the uteroglobin gene is unique in its sequence and its location overlapping a weak TATA box (TACA). Binding of YY1 was required for efficient transcription in TCF-positive Ishikawa cells, which responded only weakly to a change of TACA to TATA, although in vitro binding affinity for the TATA-box-binding protein increased by 1 order of magnitude. In contrast, in CV-1 cells, lacking TCF, binding of YY1 was not required for transcription in the context of a wild-type TACA box, whereas a change from TACA to TATA led to significantly increased reporter gene expression. DNA binding data exclude a role of YY1 in stabilizing the interaction of the TATA-box-binding protein with the uteroglobin promoter. We conclude that cell lines derived from uteroglobin-expressing tissues overcome the weak TATA box with the help of auxiliary factors, one of them being YY1.

Members of the Sp transcription factor family control transcription from the uteroglobin promoter

Previous analyses of the uteroglobin promoter revealed seven distinct regions, which contribute to its overall activity in epithelial cells from endometrium and lung. Most significantly, a mutation of the promoter sequence around 65 base pairs upstream of the transcriptional start site severely impairs promoter activity. The transcription factor acting through this sequence has not been identified yet. Here, we report that members of the Sp transcription factor family specifically recognize this non-classical GC box, in addition to another functional motif located 230 base pairs upstream of the transcriptional start site. We have characterized in detail the interaction of recombinant Sp3 with both motifs by DNase I footprinting and methylation protection using the wild-type uteroglobin promoter and various linker scanning mutants as templates. Electrophoretic mobility shift analyses show that Sp1 and Sp3 both bind with similar affinity to these elements. We demonstrate that the DNA-binding proteins in the endometrial cell line Ishikawa which recognize these motifs are also Sp1 and Sp3. Gene transfer experiments into Drosophila Schneider cells that do not contain endogenous Sp factors revealed that both DNA motifs respond to transiently expressed Sp1 and Sp3. Our results show thus that the level of transcription from the uteroglobin promoter is controlled by members of the Sp transcription factor family through unusual Sp binding sites.

Melanocyte-specific expression of the human tyrosinase promoter: activation by the microphthalmia gene product and role of the initiator

The tyrosinase gene is expressed specifically in melanocytes and the cells of the retinal pigment epithelium, which together are responsible for skin, hair, and eye color. By using a combination of DNase I footprinting and band shift assays coupled with mutagenesis of specific DNA elements, we examined the requirements for melanocyte-specific expression of the human tyrosinase promoter. We found that as little as 115 bp of the upstream sequence was sufficient to direct tissue-specific expression. This 115-bp stretch contains three positive elements: the M box, a conserved element found in other melanocyte-specific promoters; an Sp1 site; and a highly evolutionarily conserved element located between -14 and +1 comprising an E-box motif and an overlapping octamer element. In addition, two further elements, one positive and one negative, are located between positions -185 and -150 and positions -150 and -115, respectively. We also found that the basic helix-loop-helix factor encoded by the microphthalmia gene, which is essential for melanocyte differentiation, can transactivate the tyrosinase promoter via the M box and the conserved E box located close to the initiator. Since in vitro assays failed to identify any melanocyte-specific DNA-binding activity, the possibility that the specific arrangement of elements within the basal tyrosinase promoter determines melanocyte-specific expression is discussed.

Melanocyte-specific expression of the human tyrosinase promoter: activation by the microphthalmia gene product and role of the initiator

The tyrosinase gene is expressed specifically in melanocytes and the cells of the retinal pigment epithelium, which together are responsible for skin, hair, and eye color. By using a combination of DNase I footprinting and band shift assays coupled with mutagenesis of specific DNA elements, we examined the requirements for melanocyte-specific expression of the human tyrosinase promoter. We found that as little as 115 bp of the upstream sequence was sufficient to direct tissue-specific expression. This 115-bp stretch contains three positive elements: the M box, a conserved element found in other melanocyte-specific promoters; an Sp1 site; and a highly evolutionarily conserved element located between -14 and +1 comprising an E-box motif and an overlapping octamer element. In addition, two further elements, one positive and one negative, are located between positions -185 and -150 and positions -150 and -115, respectively. We also found that the basic helix-loop-helix factor encoded by the microphthalmia gene, which is essential for melanocyte differentiation, can transactivate the tyrosinase promoter via the M box and the conserved E box located close to the initiator. Since in vitro assays failed to identify any melanocyte-specific DNA-binding activity, the possibility that the specific arrangement of elements within the basal tyrosinase promoter determines melanocyte-specific expression is discussed.

Two distinct factors bind to the rabbit uteroglobin TATA-box region and are required for efficient transcription

The rabbit uteroglobin gene is expressed in a variety of epithelial cell types like the lung Clara cells and the glandular and luminal epithelial cells of the endometrium. Expression in Clara cells is on a high constitutive level, whereas expression in the rabbit endometrium is under tight hormonal control. One important element of the rabbit uteroglobin gene mediating its efficient transcription in two epithelial cell lines from human endometrium (Ishikawa) and lung (NCI-H441) is its noncanonical TATA box (TACA). Here, we show that two factors (TATA core factor [TCF] and TATA palindrome factor [TPF]) different from the TATA-box binding protein bind to the DNA major groove at two adjacent sites within the uteroglobin TATA-box region and that one of them (TCF) is specifically expressed in cell lines derived from uteroglobin-expressing tissues. The binding sites for TCF and TPF, respectively, are both required for efficient transcription in Ishikawa and NCI-H441 cells. Mutation of the TACA box, which we show is a poor TATA box in functional terms, to a canonical TATA motif does not affect TCF and TPF binding. Therefore, we suggest that the function of the unusual cytosine could be to reduce rabbit uteroglobin expression in cells lacking TCF and that the interaction of TATA-box binding protein with the weak TACA site is facilitated in TCF- and TPF-positive cells.

Two distinct factors bind to the rabbit uteroglobin TATA-box region and are required for efficient transcription

The rabbit uteroglobin gene is expressed in a variety of epithelial cell types like the lung Clara cells and the glandular and luminal epithelial cells of the endometrium. Expression in Clara cells is on a high constitutive level, whereas expression in the rabbit endometrium is under tight hormonal control. One important element of the rabbit uteroglobin gene mediating its efficient transcription in two epithelial cell lines from human endometrium (Ishikawa) and lung (NCI-H441) is its noncanonical TATA box (TACA). Here, we show that two factors (TATA core factor [TCF] and TATA palindrome factor [TPF]) different from the TATA-box binding protein bind to the DNA major groove at two adjacent sites within the uteroglobin TATA-box region and that one of them (TCF) is specifically expressed in cell lines derived from uteroglobin-expressing tissues. The binding sites for TCF and TPF, respectively, are both required for efficient transcription in Ishikawa and NCI-H441 cells. Mutation of the TACA box, which we show is a poor TATA box in functional terms, to a canonical TATA motif does not affect TCF and TPF binding. Therefore, we suggest that the function of the unusual cytosine could be to reduce rabbit uteroglobin expression in cells lacking TCF and that the interaction of TATA-box binding protein with the weak TACA site is facilitated in TCF- and TPF-positive cells.

Melanocyte-specific gene expression: role of repression and identification of a melanocyte-specific factor, MSF

For a gene to be transcribed in a tissue-specific fashion, expression must be achieved in the appropriate cell type and also be prevented in other tissues. As an approach to understanding the regulation of tissue-specific gene expression, we have analyzed the requirements for melanocyte-specific expression of the tyrosinase-related protein 1 (TRP-1) promoter. Positive regulation of TRP-1 expression is mediated by both an octamer-binding motif and an 11-bp element, termed the M box, which is conserved between the TRP-1 and other melanocyte-specific promoters. We show here that, consistent with its ability to activate transcription in a non-tissue-specific fashion, the M box binds the basic-helix-loop-helix factor USF in vitro. With the use of a combination of site-directed mutagenesis and chimeric promoter constructs, additional elements involved in regulating TRP-1 expression were identified. These include the TATA region, which appears to contribute to the melanocyte specificity of the TRP-1 promoter. Mutational analysis also identified two repressor elements, one at the start site, the other located at -240, which function both in melanoma and nonmelanoma cells. In addition, a melanocyte-specific factor, MSF, binds to sites which overlap both repressor elements, with substitution mutations demonstrating that binding by MSF is not required for repression. Although a functional role for MSF has not been unequivocally determined, the location of its binding sites leads us to speculate that it may act as a melanocyte-specific antirepressor during transcription of the endogenous TRP-1 gene.

Melanocyte-specific gene expression: role of repression and identification of a melanocyte-specific factor, MSF

For a gene to be transcribed in a tissue-specific fashion, expression must be achieved in the appropriate cell type and also be prevented in other tissues. As an approach to understanding the regulation of tissue-specific gene expression, we have analyzed the requirements for melanocyte-specific expression of the tyrosinase-related protein 1 (TRP-1) promoter. Positive regulation of TRP-1 expression is mediated by both an octamer-binding motif and an 11-bp element, termed the M box, which is conserved between the TRP-1 and other melanocyte-specific promoters. We show here that, consistent with its ability to activate transcription in a non-tissue-specific fashion, the M box binds the basic-helix-loop-helix factor USF in vitro. With the use of a combination of site-directed mutagenesis and chimeric promoter constructs, additional elements involved in regulating TRP-1 expression were identified. These include the TATA region, which appears to contribute to the melanocyte specificity of the TRP-1 promoter. Mutational analysis also identified two repressor elements, one at the start site, the other located at -240, which function both in melanoma and nonmelanoma cells. In addition, a melanocyte-specific factor, MSF, binds to sites which overlap both repressor elements, with substitution mutations demonstrating that binding by MSF is not required for repression. Although a functional role for MSF has not been unequivocally determined, the location of its binding sites leads us to speculate that it may act as a melanocyte-specific antirepressor during transcription of the endogenous TRP-1 gene.

A regulatory element within the uteroferrin gene 5'-flanking region binds a pregnancy-associated uterine endometrial protein

DNA-protein interactions within two putative regulatory regions distal from the transcription initiation site of the porcine uteroferrin (UF) gene were characterized. These regions, termed XB (-1,600 to -1,129 bp) and AB (-1,128 to -893 bp) exhibited transcriptional enhancer activities within the context of the heterologous SV40 promoter, that were specific to endometrial cells. DNase I and gel-shift assays demonstrated that both fragments contain a heptamer motif TGCTAGA that binds a nuclear protein present in crude and DEAE-fractionated nuclear extracts from porcine endometrium of pregnancy. This heptad sequence, designated as endometrial-associated sequence (EAS), is different from previously described nuclear protein-binding consensus sequences. Mutations in the heptamer motif abolished binding to the nuclear factor, as detected by gel-shift assays. The endometrial nuclear protein that interacts with the heptamer was characterized by Southwestern and UV cross-linking analysis. The protein has an approximate M(r) of 80 kD, is basic (pI 7.7-8.6) and is present in pig endometrium throughout pregnancy. The functional relevance of this DNA-binding protein in the control of UF gene transcription in the endometrium is discussed.

Chromosomal organization of the gene encoding porcine antileukoproteinase and functional analysis of the promoter region in endometrial and placental cells

The apparent preferential expression of the elastase/cathepsin G protease inhibitor antileukoproteinase (ALP) in endometrium of species with epitheliochorial placenta suggests mechanisms of transcriptional regulation unique to these mammalian species. To begin to define the cis-acting regulatory elements involved in the endometrial transcription of the ALP gene, the porcine ALP gene was isolated and characterized. The porcine gene spans at least 13 kb and consists of 5 exons and 4 introns. This genomic structure, except for an additional exon, is similar to that of the human gene where the first three exons encode the signal peptide, trypsin/cathepsin G binding region, and elastase binding region, respectively. The positions of the 16 cysteine residues in exons 2 and 3 of the human gene are conserved in the porcine gene. The porcine gene contains a TATA box at -29 nucleotide (nt), and sequences with limited homology to those which might bind the transcription factors AP-1, AP-2, Sp-1 and Oct-1. The functional promoter activity of the ALP-5' flanking DNA was examined using chimeric ALP-chloramphenicol acetyl transferase (CAT) DNA constructs, after transient transfection in human (ECC-1, Ishikawa) and rabbit (HRE-H9) endometrial and human trophoblastic (JEG-3) cell lines. A 887 nt fragment of the ALP-5'-flanking region (-887ALP-pCAT-E) was active in these cell lines, with the highest promoter activity observed in the ECC-1. Progressive 5' deletion of the 887 nt fragment up to -243 nt had no effect on CAT gene expression in all cell lines, relative to the longest construct.(ABSTRACT TRUNCATED AT 250 WORDS)

The lung-specific CC10 gene is regulated by transcription factors from the AP-1, octamer, and hepatocyte nuclear factor 3 families

We have shown that a large fragment (-2339 to +57) from the rat CC10 gene directed lung-specific expression of a reporter construct in transgenic animals. Upon transfection, a smaller fragment (-165 to +57) supported reporter gene expression exclusively in the Clara cell-like NCI-H441 cell line, suggesting that a Clara cell-specific transcriptional element resided on this fragment (B. R. Stripp, P. L. Sawaya, D. S. Luse, K. A. Wikenheiser, S. E. Wert, J. A. Huffman, D. L. Lattier, G. Singh, S. L. Katyal, and J. A. Whitsett, J. Biol. Chem. 267:14703-14712, 1992). The interactions of nuclear proteins with a particular segment of the CC10 promoter which extends from 79 to 128 bp upstream of the CC10 transcription initiation site (CC10 region I) have now been studied. This sequence can stimulate both in vitro transcription in H441 nuclear extract and transient expression of reporter constructs in H441 cells. Electrophoretic mobility shift assays using extracts from H441, HeLa, rat liver, and fetal sheep lung cells were used to demonstrate that members of the AP-1, octamer, and HNF-3 families bind to CC10 region I. Transcription factors from H441 cells which are capable of binding to CC10 region I are either absent in HeLa, rat liver, and fetal sheep lung extracts or enriched in H441 extracts relative to extracts from non-Clara cells.

The lung-specific CC10 gene is regulated by transcription factors from the AP-1, octamer, and hepatocyte nuclear factor 3 families

We have shown that a large fragment (-2339 to +57) from the rat CC10 gene directed lung-specific expression of a reporter construct in transgenic animals. Upon transfection, a smaller fragment (-165 to +57) supported reporter gene expression exclusively in the Clara cell-like NCI-H441 cell line, suggesting that a Clara cell-specific transcriptional element resided on this fragment (B. R. Stripp, P. L. Sawaya, D. S. Luse, K. A. Wikenheiser, S. E. Wert, J. A. Huffman, D. L. Lattier, G. Singh, S. L. Katyal, and J. A. Whitsett, J. Biol. Chem. 267:14703-14712, 1992). The interactions of nuclear proteins with a particular segment of the CC10 promoter which extends from 79 to 128 bp upstream of the CC10 transcription initiation site (CC10 region I) have now been studied. This sequence can stimulate both in vitro transcription in H441 nuclear extract and transient expression of reporter constructs in H441 cells. Electrophoretic mobility shift assays using extracts from H441, HeLa, rat liver, and fetal sheep lung cells were used to demonstrate that members of the AP-1, octamer, and HNF-3 families bind to CC10 region I. Transcription factors from H441 cells which are capable of binding to CC10 region I are either absent in HeLa, rat liver, and fetal sheep lung extracts or enriched in H441 extracts relative to extracts from non-Clara cells.

Cloning by recognition site screening of two novel GT box binding proteins: a family of Sp1 related genes

Previous analyses of the uteroglobin gene promoter revealed a GT1 box which is also found in the SV40 enhancer. The GT1 element in the context of the uteroglobin promoter is active in Ishikawa cells, a human endometrial cell line, but not in HeLa cells. Here we report the cloning by recognition site screening of two factors (SPR-1 and SPR-2) which bind to this GT1 motif. SPR-1 and SPR-2 are homologues of the transcription factor Sp1. All three proteins are closely related members of a gene family encoding proteins with very similar structural features. Like Sp1, SPR-1 and SPR-2 contain glutamine and serine/threonine rich amino acid stretches. Most significantly, the DNA binding domains of all three proteins are highly conserved and they recognize GT as well as GC boxes identically. SPR-2 mRNA is expressed ubiquitously, whereas SPR-1 transcripts are abundant in the brain but barely detectable in other organs. The possible function of these factors for the activity of the uteroglobin promoter is discussed.

Positive and negative elements regulate a melanocyte-specific promoter

Melanocytes are specialized cells residing in the hair follicles, the eye, and the basal layer of the human epidermis whose primary function is the production of the pigment melanin, giving rise to skin, hair, and eye color. Melanogenesis, a process unique to melanocytes that involves the processing of tyrosine by a number of melanocyte-specific enzymes, including tyrosinase and tyrosinase-related protein 1 (TRP-1), occurs only after differentiation from the melanocyte precursor, the melanoblast. In humans, melanogenesis is inducible by UV irradiation, with melanin being transferred from the melanocyte in the epidermis to the surrounding keratinocytes as protection from UV-induced damage. Excessive exposure to UV, however, is the primary cause of malignant melanoma, an increasingly common and highly aggressive disease. As an initial approach to understanding the regulation of melanocyte differentiation and melanocyte-specific transcription, we have isolated the gene encoding TRP-1 and examined the cis- and trans-acting factors required for cell-type-specific expression. We find that the TRP-1 promoter comprises both positive and negative regulatory elements which confer efficient expression in a TRP-1-expressing, pigmented melanoma cell line but not in NIH 3T3 or JEG3 cells and that a minimal promoter extending between -44 and +107 is sufficient for cell-type-specific expression. Assays for DNA-protein interactions coupled with extensive mutagenesis identified three factors, whose binding correlated with the function of two positive and one negative regulatory element. One of these factors, termed M-box-binding factor 1, binds to an 11-bp motif, the M box, which acts as a positive regulatory element both in TRP-1-expressing and -nonexpressing cell lines, despite being entirely conserved between the melanocyte-specific tyrosinase and TRP-1 promoters. The possible mechanisms underlying melanocyte-specific gene expression are discussed.

Tissue-specific and hormonally regulated expression of the puromycin N-acetyltransferase-encoding gene under control of the rabbit uteroglobin promoter in transgenic mice

Transgenic mice bearing two fragments of the rabbit uteroglobin 5'-flanking region fused to the new reporter gene (pac) encoding puromycin N-acetyltransferase (PAC) showed a different pattern of expression. Transgenic lines (C0.4) harboring a 404-bp fragment (-396/+8) had a uterus-specific expression slightly inducible by estrogen, lacking detectable expression in other tissues where the uteroglobin-encoding gene is naturally expressed in rabbit. Transgenic lines (C3.2) bearing a longer fragment of 3.2-kb (-3254/+8) showed hormonally regulated expression in the uterus and the male genital tract, and detectable expression in the lung. In addition, the nonstimulated uterine expression of the transgene was higher in C0.4 lines than in C3.2 lines. It could be concluded that all sequences required for uterus-specific expression should be present within the 404-bp fragment, and that other upstream (-396) sequences are responsible for expression in the lung and male genital tract, as well as for a possible down modulation of expression in the uterus.

Positive and negative elements regulate a melanocyte-specific promoter

Melanocytes are specialized cells residing in the hair follicles, the eye, and the basal layer of the human epidermis whose primary function is the production of the pigment melanin, giving rise to skin, hair, and eye color. Melanogenesis, a process unique to melanocytes that involves the processing of tyrosine by a number of melanocyte-specific enzymes, including tyrosinase and tyrosinase-related protein 1 (TRP-1), occurs only after differentiation from the melanocyte precursor, the melanoblast. In humans, melanogenesis is inducible by UV irradiation, with melanin being transferred from the melanocyte in the epidermis to the surrounding keratinocytes as protection from UV-induced damage. Excessive exposure to UV, however, is the primary cause of malignant melanoma, an increasingly common and highly aggressive disease. As an initial approach to understanding the regulation of melanocyte differentiation and melanocyte-specific transcription, we have isolated the gene encoding TRP-1 and examined the cis- and trans-acting factors required for cell-type-specific expression. We find that the TRP-1 promoter comprises both positive and negative regulatory elements which confer efficient expression in a TRP-1-expressing, pigmented melanoma cell line but not in NIH 3T3 or JEG3 cells and that a minimal promoter extending between -44 and +107 is sufficient for cell-type-specific expression. Assays for DNA-protein interactions coupled with extensive mutagenesis identified three factors, whose binding correlated with the function of two positive and one negative regulatory element. One of these factors, termed M-box-binding factor 1, binds to an 11-bp motif, the M box, which acts as a positive regulatory element both in TRP-1-expressing and -nonexpressing cell lines, despite being entirely conserved between the melanocyte-specific tyrosinase and TRP-1 promoters. The possible mechanisms underlying melanocyte-specific gene expression are discussed.

A combination of upstream and proximal elements is required for efficient expression of the mouse renin promoter in cultured cells

Renin, a key enzyme controlling blood pressure, is produced mainly in the kidney. To identify the transcriptional regulatory elements of the mouse Ren-1c gene, the promoter regions were fused to the CAT reporter gene and transfected into embryonic kidney-derived 293 cells and four extrarenal cell lines, HeLa, HepG2, HT1080 and NIH3T3 cells. Transient transfection assay showed that sequences from -365 to +16 of the renin gene could direct transcription of the CAT hybrid gene only in 293 cells. Deletion analysis identified two transcriptionally active regions; the renin upstream-promoter element (RU-1 element; position -224 to -138) and the renin proximal-promoter element (RP-2 element; position -75 to -47). Although the RU-1 element functioned as an activator, depending on its orientation, it failed to trans-activate the renin promoter when the RP-2 element was deleted. By contrast, the proximal element alone exhibited a weak trans-activator property. Gel shift assay identified RU-1 element-binding factors in both 293 and HeLa cells, whereas 293 cell-dominant factors were shown to bind only to RP-2 element. Therefore, both RU-1 and RP-2 elements were found to be necessary for efficient CAT expression from the renin promoter in 293 cells, suggesting that activation of the Ren-1c promoter requires combined action between cell type-dominant and ubiquitous nuclear factors.