Transfection of keratinocytes abrogates detectable DNA-binding activity of CCAAT displacement protein

Transfection of keratinocytes with plasmid DNA leads to the loss of detectable DNA-binding activity of CCAAT displacement protein but not of Yin Yang 1, as monitored by electrophoretic mobility shift assay. This phenomenon was found to be attributable to the presence of plasmid DNA in the nuclear extracts prepared from transfected cells. Treatment of these nuclear extracts with DNase I restored the ability to monitor DNA-binding activity of CDP. This report documents a new pitfall associated with transfection.