CCAAT/enhancer-binding protein delta gene expression is mediated by APRF/STAT3

Area of Science:

• Molecular Biology
• Gene Regulation
• Cellular Signaling

Background:

• CCAAT/enhancer-binding protein delta (C/EBP delta) is a transcription factor with rare basal expression.
• C/EBP delta is sharply induced early in the acute phase response.
• Understanding C/EBP delta's induction mechanisms is crucial for studying inflammatory processes.

Purpose of the Study:

• To investigate the regulatory mechanisms behind C/EBP delta gene induction.
• To identify cis-elements and trans-acting factors involved in C/EBP delta expression.
• To elucidate the role of IL-6 signaling in C/EBP delta regulation.

Main Methods:

• Isolation and functional analysis of the rat C/EBP delta gene's 5'-flanking region.
• Cell transfection assays in rat fibroblast 3Y1 cells.
• Treatment of HepG2 cells with IL-6.
• Electrophoretic mobility shift assays (EMSA) and DNA footprinting.

Main Results:

• The upstream region up to -175 bp of the C/EBP delta gene is sufficient for full basal activity.
• At least three cis-elements, including a GC box, are involved in basal activity.
• Interleukin-6 (IL-6) rapidly induces C/EBP delta mRNA in HepG2 cells.
• The binding site for APRF/STAT3 was identified within the C/EBP delta gene regulatory region.

Conclusions:

• C/EBP delta gene expression is mediated by APRF/STAT3 activation.
• APRF/STAT3 is phosphorylated via the IL-6 receptor pathway upon IL-6 treatment.
• Activated APRF/STAT3 plays a key role in trans-activating other acute phase response genes.