Repression of CD2 gene expression is mediated by an AP-2 related factor

Area of Science:

• Immunology
• Molecular Biology
• Gene Regulation

Background:

• CD2 gene expression is crucial for T cell development and tightly regulated.
• DNase I hypersensitivity sites (DHS1 and DHS2) 5' to the CD2 gene are implicated in its developmental regulation.
• DHS2 is near the minimal promoter, while DHS1 is located ~1800 bp upstream.

Purpose of the Study:

• To investigate the regulatory activities within the DHS1 region of the CD2 gene.
• To identify the DNA elements responsible for repressor and derepressor activities.
• To characterize the nuclear factors binding to these regulatory elements.

Main Methods:

• DNase I hypersensitivity analysis to map regulatory regions.
• Reporter gene assays to assess promoter activity and regulatory element function.
• Site-directed mutagenesis to probe the role of specific DNA binding sites.
• Electrophoretic mobility shift assays (EMSAs) to detect nuclear factor binding.

Main Results:

• The DHS1 region contains both repressor and derepressor activities.
• This repressor activity functions independently of orientation and affects both homologous and heterologous promoters.
• AP-2 binding site is essential for repressor activity; mutation abolishes it.
• A Jurkat cell nuclear factor binds specifically to this site, distinct from AP-2.

Conclusions:

• The DHS1 region harbors a potent repressor element critical for CD2 gene regulation during T cell development.
• An AP-2 binding site within DHS1 mediates this repression, involving a novel nuclear factor.
• These findings elucidate a key mechanism in the precise control of T cell gene expression.