I have two plasmid, one expressing tTA and the other one has a eGFP under TRE promoter. By right I would see GFP signal when both plasmids are in a cell. However when I transfected HEK293 cell with only TRE containing plasmid, there is a strong GFP signal, same level as the cells transfected with both plasmids, which means this reporter is leaky. How can I reduce the background signal? I heard antibiotic selection can do the work, but how exactly it works? Should the signal be stronger as selecting will eliminate those non-transfected cells?
Thanks in advance!