GPHN lack intrinsic transcriptional activation and repression properties. Five tandemly arrayed GAL4 recognition sites were introduced upstream of a HSV thymidine kinase (TK) promoter (A) and used to assess the effects of GPHN on transcriptional activity. X represents different genes shown in B and C. GAL4(DBD)–GPHN full and GAL4(DBD)–GPHN ex14 lack transcriptional activation (B) or repression activities (C) in transient assays. The results are presented as the fold activation or repression relative to the empty expression plasmid. The result is the average of normalized luciferase values of at least 3 independent experiments.