The human colipase gene: isolation, chromosomal location, and tissue-specific expression

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Dietary triglyceride digestion in the duodenum involves pancreatic lipase, whose activity is modulated by bile salts and colipase.
• Synthesis and secretion of lipase and colipase increase with dietary fats and secretin, suggesting gene regulation by these factors.
• Understanding the genetic regulation of colipase is essential for comprehending fat digestion processes.

Purpose of the Study:

• To investigate the regulatory mechanisms governing human colipase gene expression.
• To identify DNA elements responsible for the tissue-specific regulation of colipase.

Main Methods:

• Isolation of the human colipase gene using a cosmid library and cDNA probe.
• Localization of the gene to chromosome 6 and characterization of its structure.
• Analysis of the 5'-flanking region for regulatory elements using transient transfection assays with reporter genes (chloramphenicol acetyltransferase) in cell lines (AR42-J, HEPG2, C2C12, COS-1).
• Electrophoretic mobility shift assays to study protein-DNA interactions.

Main Results:

• The human colipase gene was isolated and mapped to chromosome 6, organized into three exons.
• The 5'-flanking region contains a TATA box, GC box, and a 28-bp sequence homologous to a rat pancreatic enhancer.
• This 28-bp region conferred tissue-specific promoter activity in AR42-J cells but not in other cell lines, indicating specific regulatory control.
• The 28-bp region specifically binds a nuclear factor.

Conclusions:

• The isolated human colipase gene possesses tissue-specific promoter activity within its 5'-flanking DNA.
• A 28-bp region in the 5'-flanking DNA is critical for directing pancreatic-specific expression and binds nuclear factors.
• These findings elucidate key aspects of colipase gene regulation, vital for fat digestion.