Expressional analysis of rabbit POU5F1 promoter region in mouse ES cells. A. Schematic view of different constructs used in the assay. B. Fluorescent activity was measured 72 hours post-nucleofection. Data was normalised with the auto-fluorescence of untreated R1 ESCs. CR1, the minimal promoter showed a weak level of basic expression in the mouse ESCs. When the proximal enhancer fragment (CR2 and CR3) was part of the regulator region the expression showed no significant change. However, when the vector containing the distal enhancer region (CR4) was co-transfected either with the minimal promoter (CR1) or with the minimal promoter and proximal enhancers (CR1+(CR2 and CR3), the expression level increased significantly. While the entire regulatory region (CR1+(CR2 and CR3)+CR4) was transfected, the expression peaked to its highest level. If compared to the Oct4-GiP cells containing the mouse CR4+CR1 region, no significant differences were found . S.E. ± values are marked on each column. Different letters mark significant differences between values (P < 0.05).