Mitogen-activated protein kinase activates human placental lactogen-B enhancer by an NF-IL6-dependent pathway.
Computer analysis of the human placental lactogen-B (hPL-B) enhancer reveals two putative binding sites for the transcription factor NF-IL6, but the role of NF-IL6 in the regulation of the enhancer is unknown. Using gel mobility shift and supershift assays, we demonstrated that NF-IL6 binds to both enhancer sites. Transient transfection studies indicated that the transcription factor NF-IL6 stimulates hPL-B enhancer activity by 4.4-fold in primary cultures of human trophoblast cells and by 32.0- and 8.4-fold in JAR and BeWo choriocarcinoma cells, respectively. Overexpression of MEK (mitogen-activated protein [MAP] kinase kinase), which is known to stimulate phosphorylation of NF-IL6, induced a 3.6-fold increase in hPL-B enhancer activity. The induction by MEK was completely inhibited by an expression plasmid for a dominant/negative mutant of NF-IL6 or by mutation of the NF-IL6 binding sites on the enhancer. PD98059, an inhibitor of MEK, inhibited hPL release from cultured trophoblast cells by about 50%. Taken together, these results indicate that MAP kinase stimulates the hPL-B enhancer by an NF-IL-6-dependent pathway.
Brar
A K
AK
Department of Pediatrics, University of Cincinnati College of Medicine, Children's Hospital Research Foundation, OH 45229-3039, USA. anoop.brar@chmcc.org
Richards
R G
RG
Cheng
Y H
YH
Richardson
B
B
Kanda
Y
Y
Handwerger
S
S
D022762:CCAAT-Enhancer-Binding Proteins; D002478:Cells, Cultured; D002822:Choriocarcinoma; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000494:pharmacology*; D004742:Enhancer Elements, Genetic; D005260:Female; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000494:pharmacology*; D009687:Nuclear Proteins / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D010928:Placental Lactogen / Q000235:genetics*; D011247:Pregnancy; D015533:Transcriptional Activation / Q000187:drug effects*; D014162:Transfection; D014327:Trophoblasts / Q000378:metabolism; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010928:Placental Lactogen; D020928:Mitogen-Activated Protein Kinases