Fig. 1

Schematic illustration of the consequences of the orientation reversal of an hypothetical, non-palindromic cis-regulatory transcription factor binding site motif. As the motif sequence is reversed in sequence direction on the opposing strand creating a reverse-complemented version of the original motif, an identical DNA interaction surface is created, but the associated transcription factor (TF) is required to bind in a 180° rotated orientation. As the TF may be asymmetric and possibly additional protein factors (denoted by light-red circles) associate non-symmetrically, the binding orientation relative to the transcription start site (TSS) of the downstream gene is reversed