Co-transfection with pCMV5 plasmids (help!!)

Alexey Merz alexey at
Wed Apr 22 14:59:19 EST 1998

> Xiaomin Fan wrote:
> > 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!
> Squelching. Both vectors use the CMV Major Immediate Early Promoter and
> you're most likely seeing the titration of limiting transcriptional
> activators.
> See, e.g.,  Gill & Ptashne (1988) _Nature_ 334:721.
Alexey Merz | URL: | email: alexey at
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