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

To identify regulatory elements in the promoter of a human placental lactogen gene (hPL3) that are important for its transcriptional activation, sequences 5' to the start of transcription were linked to the reporter gene chloramphenicol acetyltransferase (CAT) and transiently transfected into JEG-3 cells, a human placental choriocarcinoma cell line. In the presence of the hPL3 enhancer, deletion of the promoter sequence between -142 and -129 basepairs resulted in an 8-fold decrease in CAT activity. Similar results were seen with the SV40 enhancer and the hPL3 promoter in HepG2 liver cells. Nuclear proteins from HepG2, HeLa, and JEG-3 cells formed specific binding complexes with this region of the hPL3 promoter by a gel mobility shift assay, indicating that the DNA-binding protein was not tissue specific. The -142 to -129 basepair region contains a sequence similar to that of a variant binding site for the transcription factor Sp1. An oligonucleotide containing Sp1-binding sites specifically competes for proteins binding the hPL3 promoter, and the methylation interference pattern is similar to that for an Sp1-binding site. This suggests that the hPL3 promoter binds Sp1- or an Sp1-like trans-acting factor, and this binding site is important for transcriptional regulation by the hPL3 enhancer in PL-producing cells.
 ...
PMID:DNA sequences involved in the transcriptional activation of a human placental lactogen gene. 196 88

Earlier studies from our laboratory indicated that apolipoprotein A-I (Apo A-I) stimulates the acute release of human placental lactogen (hPL) from trophoblast cells in culture. We have now demonstrated that Apo A-I also causes a secondary increase in hPL release, beginning about 6 h after exposure to Apo A-I, that is blocked by cycloheximide and actinomycin D. Apo A-I also stimulated a dose-dependent increase in hPL promoter activity in JAR cells transfected with a 1.1-kilobase (-1078/2) fragment of the hPL3 promoter coupled to a chloramphenicol acetyltransferase (CAT) reporter gene. Maximal stimulation, 5.2-fold above basal levels, occurred at an Apo A-I concentration of 1.5 mg/ml, which is within the physiological concentration of Apo A-I during pregnancy. 37pA, a synthetic amphipathic peptide that mimics the secondary structure of Apo A-I and stimulates the synthesis and release of hPL, also stimulated a dose-dependent increase in CAT activity, with maximal stimulation comparable to that caused by Apo A-I. In addition, Apo A-I stimulated a modest increase in CAT activity in BeWo choriocarcinoma cells, Chinese hamster ovary cells, and HeLa cells. However, the maximal stimulation of hPL promoter activity in the Chinese hamster ovary and HeLa cells (approximately 2.5-fold above basal levels) was less than that in choriocarcinoma cells, suggesting that trophoblast cell nuclear factors may be necessary for maximal expression of the promoter in response to Apo A-I. Taken together, these results indicate that Apo A-I stimulates hPL gene expression, and that DNA elements in the first 1.1 kilobase of the promoter are sufficient for transactivation by Apo A-I.
 ...
PMID:Apolipoprotein A-I stimulates placental lactogen expression by human trophoblast cells. 758 8

In this study, we have demonstrated that retinoic acid (RA) and thyroid hormone (T3) stimulate the synthesis and release of human placental lactogen (hPL), one of the major secretory products of syncytiotrophoblast cells. Enzymatically, dispersed trophoblast cells from term placentas exposed continuously to RA (0.5 microM) and T3 (0.1 microM) for 5 days released significantly more hPL than control cells after 3 days of exposure (P < 0.001 in each instance). On days 4 and 5, the amounts of hPL released by cells exposed to RA and T3 were approximately 3- and 5-fold higher than those in control cells, respectively. The stimulation by both RA and T3 was dose dependent and was accompanied by stimulation of hPL messenger RNA levels. RA and T3 caused 3.5- and 5.6-fold increases, respectively, in chloramphenicol acetyltransferase activity in BeWo choriocarcinoma cells transfected transiently with a 2.3-kilobase (kb) fragment of the hPL promoter (-2300 to 2 basepairs) coupled to a chloramphenicol acetyltransferase reporter gene. Deletion construct analysis of the hPL promoter (2.3, 1.2, and 0.5 kb) indicated that the T3- and RA-responsive elements are localized -0.5 to -1.2 kb up-stream from the transcriptional start site (+1), where several consensus RA- and T3-responsive element sites are present. These results indicate that RA and T3 stimulate the synthesis and release of hPL by a mechanism involving hPL gene transcription and further support a role for these steroids in placental function.
 ...
PMID:Retinoic acid and thyroid hormone regulate placental lactogen expression in human trophoblast cells. 786 2

The human placenta synthesizes 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and expresses the vitamin D receptor (VDR), but the roles of 1,25-(OH)2D3 and the VDR in placental physiology are poorly understood. In this study, we have demonstrated that 1,25-(OH)2D3 stimulates the synthesis and release of human placental lactogen (hPL), one of the major secretory products of syncytiotrophoblast cells. Enzymatically dispersed trophoblast cells from term placentas exposed continuously to 1,25-(OH)2D3 (0.1, 6, and 37 microM) for 5 days released significantly more hPL than control cells after the third day of exposure. On days 4 and 5, the amounts of hPL released by cells exposed to 1,25-(OH)2D3 were 2.54- and 4.14-fold that of control cells (P < 0.001 in each instance). The stimulation by 1,25-(OH)2D3 was dose dependent and was accompanied by stimulation of hPL messenger RNA levels. Transient transfection studies of BeWo choriocarcinoma cells transfected with hPL promoter constructs coupled to the chloramphenicol acetyltransferase reporter gene indicated that the stimulation of hPL expression is due at least in part to stimulation of hPL gene expression. Deletion analysis studies of the hPL promoter indicated that a region between -500 to -1200 basepairs is necessary for 1,25-(OH)2D3 responsiveness. Analysis of this region shows a consensus vitamin D response element (VDRE) DNA-binding site of a direct repeat motif separated by three bases. Ligation of this placental VDRE site into a heterologous chloramphenicol acetyltransferase vector caused 1,25-(OH)2D3 responsiveness. Moreover, mobility shift assays demonstrated binding of VDR to placental VDRE. These results indicate that 1,25-(OH)2D3 stimulates the synthesis and release of hPL by a mechanism involving hPL gene transcription and support a role for vitamin D and the VDR in placental function.
 ...
PMID:Regulation of human placental lactogen expression by 1,25-dihydroxyvitamin D3. 798 55

Interleukin-6 (IL-6) stimulates the release of hCG from syncytiotrophoblast cells, but the effects of IL-6 and other cytokines on the release of placental lactogen (hPL) are unknown. To determine the effect of IL-6 on hPL release, we exposed an enriched fraction of trophoblast cells (prepared by the isopycnic centrifugation of enzymatically dispersed term placenta) continuously to IL-6 (500 U/ml) for up to 6 days. The amounts of hPL released by the IL-6-exposed cells during days 3 and 6 were 177.6 +/- 2.4% and 267.5 +/- 12.6% that of control cells, respectively (P < 0.0001 in each instance). In addition, the hPL messenger RNA (mRNA) contents of the IL-6-exposed cells after 3 and 6 days of exposure were 2.2- and 4.7-fold that of control cells. The stimulatory effect of IL-6 on hPL release and hPL mRNA levels was dose dependent, with a minimal effective dose of 50 U/ml. IL-1 beta, which is known to stimulate IL-6 production by human trophoblast cells, also stimulated dose-dependent increases in hPL release and hPL mRNA levels. IL-6 (500 U/ml) had no effect on trophoblast differentiation, but stimulated a 20-fold increase in hPL promoter activity in BeWo choriocarcinoma cells transfected transiently with a plasmid containing 2.3 kilobases of the hPL promoter coupled to the chloramphenicol acetyltransferase gene. In addition, BeWo cells exposed to IL-6 (500 U/ml) for 3 and 6 days contained 2.4- and 3.2-fold more hPL mRNA levels than control cells. Because placental macrophages and syncytiotrophoblast cells release IL-6, these results strongly suggest an autocrine/paracrine role for IL-6 in the regulation of hPL release. The increase in hPL release appears to be due at least in part to an increase in hPL gene expression.
 ...
PMID:Interleukin-6 stimulates placental lactogen expression by human trophoblast cells. 803 20