Does anybody knows what is an additional factor which facilitates to the high GFP expression in pCAGGS (except of CAG promoter) ? I have constructed a vector where I`ve use a CAG prooter, but still have half expression ratrer than in pCAGGS.
The pCAGGS vector also carries the Neo selection gene under the weak tk promoter, so only cells that have multiple copies will survive. That could be the reason why you observe higher GFP expression with pCAGGS.
Thank you ! You are right, it is one of the reason of high GFP expression, however my backbone also contains the same gene. Meanwhile I found the solution But I really appreciate your answer !