Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study is an attempt to determine whether estrogen could directly regulate human gonadotropin-releasing hormone (GnRH) gene expression. Human GnRH expression vectors were constructed by fusing various 5' flanking regions of the human GnRH gene upstream of the luciferase reporter gene (LUC) or the thymidine kinase promoter linked to the chloramphenicol acetyltransferase reporter gene (CAT). These constructs were transiently transfected into a human choriocarcinoma cell line (JEG-3) and LUC or CAT activity was measured after either no treatment or treatment with various concentrations of estradiol. A stimulatory estrogen response element (ERE) was localized to a 32-bp region between -547 and -516 bp. To determine whether estrogen receptor bound to this region of the gene, we performed DNase I footprinting using purified calf uterine estrogen receptor. DNase I footprinting demonstrates a strong footprint between -567 and -514 bp of the human GnRH gene. In addition, an avidin-biotin complex DNA-binding assay demonstrated that a biotinylated DNA fragment containing -541 to -517 bp of the human GnRH gene bound 35S-labeled estrogen receptor as well as a biotinylated DNA fragment containing the xenopus vitellogenin ERE. On the other hand, the negative control biotinylated DNA fragment derived from adenovirus 5 bound insignificant amounts of 35S-labeled estrogen receptor. Both the GnRH ERE and vitellogenin ERE bound 35S-labeled estrogen receptor with high affinity (approximately 1 nM). These data indicate that the human GnRH gene contains an ERE sufficient to mediate a stimulatory response to estrogen in heterologous cells. Based upon these data we hypothesize that the human GnRH gene might also be directly regulated by estrogen in the hypothalamus, and that this regulation may explain the GnRH hypersecretion observed at the time of the preovulatory luteinizing hormone (LH) surge.
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PMID:Evidence for direct estrogen regulation of the human gonadotropin-releasing hormone gene. 193 51

Prostaglandin endoperoxide synthase isoform 2 (PGS-2) mRNA and protein are transiently induced by gonadotropins in granulosa cells of preovulatory follicles prior to ovulation. To better understand the hormonal regulation of the rat PGS-2 (rPGS-2) gene in these cells, genomic clones containing rPGS-2 as well as up to 6 kilobases of 5'-flanking DNA were isolated by screening a rat liver genomic library with a labeled 5'-fragment of the mouse PGS-2 cDNA. Primer extension analysis using ovarian follicular mRNA identified the presence of a single rPGS-2 transcription initiation site located 144 nucleotides upstream of the ATG translation initiation codon. To test for promoter activity within the 5'-flanking region of the rPGS-2 gene, a genomic fragment, -2698/32 (1 = cap site), as well as a series of 5'-deletion mutants, were fused upstream of the chloramphenicol acetyltransferase (CAT) reporter gene and transfected into primary cultures of granulosa cells. Forskolin (7.5 microM), follicle-stimulating hormone (500 ng/ml) and luteinizing hormone (500 ng/ml) induced CAT activity following transfection with the -2698/32PGS.CAT, whereas gonadotropin-releasing hormone (10(-6) M) and interleukin-1 beta (30 ng/ml) had no effect. Deletion mutants delineated the region spanning from -192 to -54 of the transcription start site to be essential for both basal and forskolin-regulated expression of the reporter gene. The same DNA fragment (-192/-54) exhibited specific binding to granulosa cell nuclear extract proteins as analyzed by electrophoretic mobility shift assays. Additional specific bands were observed in extracts prepared from granulosa cells exposed to an ovulatory dose of gonadotropin. Collectively, these results provide the first structural and functional evidence that the transcriptional regulation of the rat PGS-2 gene by gonadotropins and forskolin in granulosa cells involves 5'-flanking DNA sequences, specifically a region between -192 and -54 of the transcription initiation site.
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PMID:Characterization and hormonal regulation of the promoter of the rat prostaglandin endoperoxide synthase 2 gene in granulosa cells. Identification of functional and protein-binding regions. 850 40

Regulated synthesis of luteinizing hormone (LH) requires coordinated transcriptional control of the alpha and LHbeta subunits in pituitary gonadotropes. Several cis-acting elements and trans-acting factors have been defined for control of the LHbeta promoter through heterologous cell culture models. In this report, we describe the identification of bipartite NF-Y (CBF/CP1) binding sites within the proximal bovine LHbeta promoter. When multimerized, one of these sites activates the heterologous, minimal HSV thymidine kinase promoter in the gonadotrope-derived cell line alphaT3-1. The functional role of the promoter-distal site in regulating the full-length bovine LHbeta promoter was assessed in vivo using transgenic mice harboring a mutant promoter linked to the chloramphenicol acetyltransferase reporter gene. While this element is important for conferring high level activity of the LHbeta promoter in pituitary, it does not appear to be essential for mediating gonadotropin-releasing hormone (GnRH) regulation. This is the first characterization of a cis-acting element within this GnRH-dependent promoter that is restricted to regulating basal expression and not GnRH-induced activity.
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PMID:An NF-Y binding site is important for basal, but not gonadotropin-releasing hormone-stimulated, expression of the luteinizing hormone beta subunit gene. 1077 13