Fig. 4. KEN selectively regulates STAT92E targets depending on the binding sites present. (A) In vitro selection experiments have defined the optimal DNA-binding sites of KEN and STAT92E. The `core' positions essential for binding are shown in red (for KEN) or green (for STAT92E). There is overlap in the sequences recognised. (B) Reporters differing only in their STAT92E-binding sites respond differently to the activity of STAT92E and KEN. In reporters to which only STAT92E can bind (green; top row), activation by STAT92E cannot be modulated by KEN. When both STAT92E and KEN are able to bind to a reporter (green and red; lower row), activation by STAT92E can be countered by the co-expression of KEN. Neither reporter is active in the absence of STAT92E. Green tick represents activation of reporter transcription, red cross implies repression.