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Activator protein-2 regulates human placental lactogen gene expression
B D Richardson1, R A Langland, C J Bachurski
1Department 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
Molecular and Cellular Endocrinology
|March 15, 2000
Summary
The activator protein-2 (AP-2) transcription factor plays a key role in regulating human placental lactogen-A (hPL-A) gene expression. AP-2 binding sites within the hPL-A promoter are crucial for its activity.
Area of Science:
- Molecular Biology
- Genetics
- Endocrinology
Background:
- Human placental lactogen-A (hPL-A) is a crucial hormone produced during pregnancy.
- Understanding the regulation of hPL-A gene expression is vital for comprehending placental function.
Purpose of the Study:
- To identify regulatory elements and transcription factors involved in controlling hPL-A gene expression.
- To elucidate the specific roles of AP-2 and Nuclear Factor I (NFI) in hPL-A promoter activity.
Main Methods:
- DNase I footprinting analysis to map protected regions on the hPL-A promoter.
- Electrophoretic mobility shift assays (EMSA) and supershift assays to identify protein-DNA interactions.
- Transient transfection assays with mutated hPL-A promoter constructs.
- Gene expression studies involving overexpression of transcription factors.
Main Results:
- Five protected regions were identified in the proximal hPL-A promoter, with two (FP4 and FP5) homologous to human growth hormone (hGH) promoter regions.
- FP4 binds both AP-2 and NFI, while FP5 binds AP-2 alone.
- Mutations in AP-2 binding sites significantly reduced hPL-A promoter activity (60-80%), whereas NFI site mutation had minimal impact.
- Overexpression of AP-2 increased hPL-A promoter activity in HepG2 cells.
Conclusions:
- The transcription factor AP-2 plays a critical and essential role in the transcriptional regulation of the hPL-A gene.
- Specific AP-2 binding sites within the hPL-A promoter are vital for its functional activity.
- NFI binding to the hPL-A promoter appears to have a less significant role compared to AP-2 in trophoblast cells.