E L3MBTL3, but neither L3MBTL3-Δ(1-64) nor L3MBTL3-Δ(SAM), represses HES1. Expression analysis of HES1 upon overexpression of LacZ control (Control), L3MBTL3, L3MBTL3-Δ(1-64) or L3MBTL3-Δ(SAM) mutants in L3MBTL3 KO U87-MG cells. Shown are means ±s.d. of triplicate experiments. P values were estimated via a one-way ANOVA on log-transformed data. NS: Not Significant. WB: Western blot; IP: immuno-precipitation. We note that in the context of this experiment, i.e., in the absence of endogenous L3MBTL3, the overexpression of L3MBTL3-Δ(1-64) does not result in the increased expression of HES1, contrasting with the result obtained in Fig 4G, i.e., in the presence of endogenous L3MBTL3. Indeed, as expected, the dominant negative effect of L3MBTL3-(1-64) on endogenous WT L3MBTL3's ability to repress the expression of Notch target genes can only be observed when WT L3MBTL3 is expressed. 