problem with pGL3basic luc activity - (Sep/10/2012 )

I have some problem because the pGL3basic alone (transfected into hela cells) answers to dose dependant assay. I tried with different doses of expression vector for the expression of the cjun protein which repress the basal activity of the pGL3basic.I obtained the same results when I cloned the promoter of my gene. I can't conclude the results of my transfection.I don't know if the repressive effect that I observed with cjun is due to the promoter of my gene or is due to the pGL3basique.
anyone had the same problem with pGL3basique
anyone can help?
thanks

pGL3 has relatively high background activity which can be inducible upon stimulation with exogenous agents. I think its because of some kind of cryptic promoter activity. I know that pXPG-Luc has lower background activity (like 20 x lower than pGL3 Basic in HEK293 T) but also I strongly suspect the new version pGL4 Basic is better as well. pXPG is avaialble from Peter Cockerill and pGL4 from Promega.

Here is a useful reference:

http://www.ncbi.nlm.nih.gov/pubmed?term=pXPG%20Cockerill

Thanks for your response . I will try the new version pGL4.