Activator protein-2 regulates human placental lactogen gene expression.
DNase I footprint analysis of the human placental lactogen-A (hPL-A) promoter using nuclear extracts from purified human trophoblast cells and BeWo choriocarcinoma cells revealed five protected regions within the proximal 325 bp. Two of the protected regions, FP4 (-289--267) and FP5 (-167--154), are homologous to regions on the human growth hormone (hGH) promoter that bind transcription factors AP-2 and/or NFI. Competitive gel shift assays and supershift assays indicated that FP4 forms complexes with activator protein-2 (AP-2) and nuclear factor I (NFI), while FP5 forms a complex with AP-2 alone. In transient transfection studies in human trophoblast cells, hPL promoter constructs containing point mutations in the AP-2 binding sites of FP4 and/or FP5 were 60-80% less active than plasmids containing the wild-type promoter. A mutation in the NFI binding site of FP4, however, had little effect on promoter activity in these cells. Overexpression of AP-2 in HepG2 cells co-transfected with the wild-type hPL promoter resulted in a significant increase in promoter activity. Taken together, these findings suggest a critical role for AP-2 in the regulation of hPL gene expression.
Richardson
B D
BD
Department of Pediatrics, University of Cincinnati College of Medicine, Division of Endocrinology, Children's Hospital Medical Center, Cincinnati, OH 45229-3039, USA. brian.richardson@chmcc.org
Langland
R A
RA
Bachurski
C J
CJ
Richards
R G
RG
Kessler
C A
CA
Cheng
Y H
YH
Handwerger
S
S
D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D010928:Placental Lactogen / Q000235:genetics*; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000494:pharmacology*; D014162:Transfection; D014327:Trophoblasts / Q000187:drug effects / Q000378:metabolism
D017931:DNA Primers; D004268:DNA-Binding Proteins; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D010928:Placental Lactogen