Protein-DNA interactions during phenotypic differentiation

Area of Science:

• Neuroscience
• Molecular Biology
• Gene Regulation

Background:

• Neuronal differentiation involves a multipotent precursor developing a specific transmitter phenotype.
• The 5' proximal regulatory region of the rat enkephalin (rENK) gene contains critical cis-elements (AP2, CREB, NF1, NFkB).

Purpose of the Study:

• To investigate the role of the rENK gene's 5' proximal regulatory cassette in developmental regulation of the enkephalin phenotype.
• To identify protein-DNA interactions within this regulatory region during neurodifferentiation.

Main Methods:

• Transient transfection assays in primary developing spinal cord neurons treated with tetrodotoxin (TTX).
• Electrophoretic mobility shift assays (EMSA) using nuclear proteins from distinct brain regions and cell lines (C6 glioma, HeLa).
• RT-PCR to assess enkephalin expression.
• Use of synthetic probes for consensus and ENK-specific motifs.

Main Results:

• The proximal regulatory region conferred activity-dependent expression in developing neurons.
• Low abundance protein-DNA complexes were detected in developing brain nuclear extracts, but not adult; patterns lacked correlation with rENK expression.
• Specific, abundant complexes formed with HeLa cell nuclear extracts, irrespective of rENK expression, while other ENK-specific motifs showed no binding.

Conclusions:

• Developmentally regulated, cell-specific expression of the rENK gene likely requires interactions with distant regulatory regions and their binding proteins.
• While the proximal region may govern inducibility via common cis-elements, cell-specific induction mechanisms remain unclear.