Relative promoter strength - (Sep/27/2011 )

Hi all, I had been transfecting 293ts using a plasmid with a CMV promoter and have recently changed to a different plasmid with a hEF1a promoter and I'm observing significant differences between these two plasmids. Do people know the relative strengths of promoters? From what I've seen I'd expect hEF1a to be a stronger promoter than CMV but am hoping to get some outside opinions on this.

Any other explanations people have for this would also be greatly appreciated.

Thanks

You can check this file for some comparisons of promoter strength. Although the comparison between EF1a and CMV is not studied for 293T cells, most of the times CMV is stronger than EF1a

http://tools.invitrogen.com/content/sfs/productnotes/F_071215_MammalianExpressionVectors.pdf

In my experience, the CMV promoter is stronger than the EF1a promoter in 293T cells, but I never quantified this, so I'm only making an 'educated' guess. Is it the same cDNA which is cloned in the vectors you are using?

Another article describes the relative strength of a number of promoters in several cell types.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010611
As you may know a list of factors determines the final out put, which is the amout of protein in the cell. Promoter sequence is only one of these factors.
Thus, it is highly recomemded to optimized the conditions for every single gene of interest. We know that most of the it's not possible in the lab, because of time, money and experience limitations.
But some companies do perform a screening of conditions. So it's recomended to look if any of the companies produce you protein. Some relevant details and even protocols sometimes are available.