NF-kappaB binds to a polymorphic repressor element in the MMP-3 promoter

Area of Science:

• Molecular Biology
• Genetics
• Cell Signaling

Background:

• A polymorphic site (5T/6T) in the matrix metalloproteinase-3 (MMP-3) promoter acts as a repressor element.
• The 6T allele is linked to reduced MMP-3 expression compared to the 5T allele.
• Zinc-binding protein-89 (ZBP-89) interacts with this site but activates the promoter upon overexpression.

Purpose of the Study:

• To investigate the molecular mechanisms underlying MMP-3 promoter regulation by the 5T/6T polymorphism.
• To identify proteins binding to the polymorphic site in response to interleukin-1 (IL-1) stimulation.
• To elucidate the role of NF-kappaB and ZBP-89 in MMP-3 gene expression.

Main Methods:

• Yeast one-hybrid assay for ZBP-89 cloning.
• Nuclear extract analysis from IL-1-stimulated human gingival fibroblasts.
• Electrophoretic mobility shift assays (EMSAs) to study protein-DNA interactions.
• Recombinant protein binding studies.

Main Results:

• The 5T/6T polymorphic site in the MMP-3 promoter is bound by p50 and p65 subunits of NF-kappaB in IL-1-stimulated cells.
• ZBP-89 also binds to this site.
• Recombinant p50 protein demonstrates preferential binding to the 6T allele.
• NF-kappaB binding is consistent with a role in limiting cytokine-induced MMP-3 expression.

Conclusions:

• NF-kappaB, in conjunction with ZBP-89, binds to the MMP-3 promoter's polymorphic site.
• The preferential binding of p50 to the 6T allele suggests a mechanism for allele-specific regulation of MMP-3 expression.
• These findings support a role for NF-kappaB in modulating MMP-3 transcription in response to inflammatory signals.