The human placental lactogen genes: structure, function, evolution and transcriptional regulation

Area of Science:

• Reproductive biology
• Endocrinology
• Molecular genetics

Background:

• Human placental lactogen (hPL) is a crucial hormone produced by the placenta.
• It belongs to a gene family including human growth hormone (hGH) and human prolactin (hPRL).
• hPL influences fetal development and maternal metabolic adaptations.

Purpose of the Study:

• To investigate the regulatory mechanisms controlling human placental lactogen (hPL) gene expression.
• To identify factors responsible for the placenta-specific high-level production of hPL.

Main Methods:

• Analysis of transcriptional and post-transcriptional regulatory controls.
• Identification of transcription factors and enhancer elements involved in hPL gene regulation.
• Examination of protein-promoter interactions and RNA stability.

Main Results:

• Two hPL genes (hPL3 and hPL4) encode identical proteins, producing 1-3 g/day.
• Post-transcriptional regulation via RNA stability influences hPL3 vs. hPL4 levels.
• Placenta-specific enhancers and transcription factors like Sp1 are critical for hPL transcription.
• Enhancer-protein interactions, involving placental-specific proteins and TEF-1 motifs, drive high-level placental expression.

Conclusions:

• Placental expression of hPL is tightly regulated by a combination of transcriptional and post-transcriptional mechanisms.
• Enhancer-protein interactions are key drivers of the high levels of hPL produced in the placenta.
• Understanding these regulatory pathways is vital for comprehending fetal-maternal interactions and placental function.