Expression of a luciferase reporter gene linked to the DEAF1 promoter was repressed in HEK293T cells by co-expressed WT DEAF1, but not by co-expressed DEAF1 variants p.G212S, p.W234R, p.R246T or p.K305del. A DEAF1 SAND domain variant, ADWA, located within the KDWK DNA binding motif and previously shown to be defective in transcriptional repression activity [Bottomley et al., 2001; Vulto-van Silfhout et al., 2014], was used as a control. Each bar represents the mean +/− SEM of the normalized luciferase activities from at least three independent experiments with the activity of the DEAF1 promoter co-transfected with the control plasmid pcDNA3 set to 1. Data were analyzed by one-way ANOVA followed by Dunnett’s multiple comparison post hoc test. *p < 0.01 for expression in the presence of co-expressed DEAF1 variants vs. WT DEAF1. Co-expression of the previously identified DEAF1 variant p.R226W did not show a significant difference in repression activity compared to WT DEAF1.