Functional characterization of MCEs in the Rab3A locus by Luciferase assay. (a) Gene structure of Rab3A is illustrated at the top and the transcription start site of the ST is designated as +1. (b, c) Presence of MCE3 induces Luciferase expression. The schematic representation of deletion constructs fused with pGL Luciferase reporter containing the Firefly Luciferase coding sequence (green block) but no promoter region. Corresponding Luciferase activity of each construct was measured in Neuro2a cells (blue bars), HEK293 cells (red bars) and Hela cells (yellow bars). The relative Luciferase activity was calculated by normalizing Firefly Luciferase activity to an internal control, Renilla Luciferase activity. Bars in the plot represent the mean of three independent experiments and the average standard deviation is indicated as error bars. (d, e) MCE1 and MCE2 increase Luciferase activity under the control of Rab3A promoter. (f, g) The effect of MCE1 and MCE2 is independent of the Rab3A promoter. The Luciferase construct of MCE1 or MCE2 was generated under the control of the SV40 promoter (yellow block). (h, i) MCE4 decreases Luciferase activity in three cell lines. (j, k) MCE5 under the control of the SV40 promoter (yellow block) and SV40 enhancer (orange block) decreases Luciferase activity in three cell lines.