Purification and preliminary characterization of a cardiac Kv1.5 repressor element binding factor

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Kv1.5 gene expression is regulated by a silencer element.
• This silencer, Kv1.5 repressor element (KRE), contains a dinucleotide-repetitive sequence.
• KRE exhibits cell-specific activity, notably in GH3 cells and cardiac tissue.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the cell-specific regulation of Kv1.5 gene expression.
• To identify the DNA-binding proteins interacting with the Kv1.5 repressor element (KRE).
• To elucidate the role of these interactions in controlling Kv1.5 promoter activity.

Main Methods:

• Electromobility gel shift assays (EMSAs) were used to detect DNA-protein complexes.
• Nuclear extracts from various cell types (GH3, CHO, COS-7) and tissues (heart, liver) were employed.
• Magnetic DNA affinity purification and UV cross-linking identified the KRE binding factor (KBF).

Main Results:

• EMSAs revealed a unique DNA-protein complex with KRE in GH3 cells and heart extracts, absent in other cell types.
• A 52-bp fragment containing a dinucleotide repeat was sufficient for silencer activity.
• A 27-kDa KRE binding factor (KBF) was identified in GH3 nuclear extracts and shown to bind KRE specifically.

Conclusions:

• The Kv1.5 repressor element (KRE) and its binding factor (KBF) are key regulators of Kv1.5 gene expression.
• KBF plays a critical role in mediating the GH3- and cardiac-specific expression of Kv1.5.
• This interaction highlights a novel mechanism for cell-specific gene regulation.