Has anyone experienced that repression of one gene's expression by another
in transienct co-transfection? I transfected 293 cells with two plasmids:
one is pCMV5 (or pFLAG-CMV-2, let's call it A ), and the another is pcDNA3
(let's call it B). When the pCMV5 construct is transfected alone in 293
cells, it expresses the gene (A) very well. However, when I co-tranfected
the pCMV5 along with the pcDNA3 construct(B), the expression of A is
decreased >90%. This repression does not happen, when a different pcDNA3
construct (let's call it C) was used to co-transfect with A in 293 cells.
So the effect seems to be gene B specific. Since B is a signaling molecule
with unclear function, I am wondering, if B modulates a signal pathway
which leads to a regulation of A expression from pCMV5 vector. If this is
the case. does anyone know if pCMV5 vector bears any responsive element
which can be regulated?
I have tried to use different cell lines, but expression of these genes
were so poor, I couldn't do any assay based on that.
Any suggestion will be greatly appreciated!