A tissue-specific nuclear factor binds to multiple sites in the human insulin-gene enhancer

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• The human insulin gene requires precise regulation for proper insulin production.
• Understanding the transcription factors that bind to the insulin gene is crucial for elucidating cell-specific expression.

Purpose of the Study:

• To identify and characterize sequence-specific DNA-binding proteins interacting with the 5' regulatory region of the human insulin gene.
• To determine the functional significance of these interactions in insulin-producing cells.

Main Methods:

• Gel-retardation assays were employed to detect protein-DNA interactions.
• Methylation-interference analysis was used to pinpoint specific binding sites.
• Mutational analysis of potential binding sites was performed.

Main Results:

• Specific nuclear factor binding was detected at nucleotides -210 to -217 and -77 to -84 within the insulin gene's 5' region.
• A conserved sequence motif 5'-C(T/C)CTAATG-3' was identified as a high-affinity binding site.
• This binding activity was observed in insulin-producing cell lines (RINm-5F, HIT.T15) but not in non-insulin-producing cell lines (HeLa, HL60).

Conclusions:

• A specific nuclear factor binds to a conserved DNA sequence in the human insulin gene's regulatory region.
• This binding is cell-specific to insulin-producing cells, suggesting a role in transcriptional regulation.
• The conserved nature of this element highlights its importance in maintaining insulin gene expression across species.