In vitro display of DNA elements that modulate the RNA transcription in cis or in trans directions

Identification of DNA elements that modulate gene expression routinely involves transfer of a reporter gene construct into appropriate host cells via high efficiency DNA transfection. Here we report the in vitro display of transcription modulating DNA elements that does not require DNA transfection and, thus, is not limited to transfectable host cells. The procedure is applicable to cis-acting promoters and, furthermore, to those DNA elements that act in trans over far distances, e.g., trans-acting enhancer and silencer DNA elements. The in vitro display is based on the in vitro transcription of the reporter DNA construct and on a quantitative display of the amount of synthesized reporter RNA compared to an internal standard. Compared to the classical procedure the in vitro display extends the analyses to both trans-acting DNA elements and a broad range of host cells.