same promoter for insert and resistance?? - need a new promoter for zeocin resistance (Nov/19/2010 )

hi there.

i want to create a stable cell line. problem is that the cells have already been immortalized with sv40 large t antigen. So i cannot use sv40 promoter since this would lead to episomal replication.
I need to use zeocin-resistance for selection, because my cells already have g418 resistance.
we have the zeocin-resistance-gene on another vector (pBudCE4.1), but under control of sv40 promoter.
I want to clone this resistance in pcDNA3.1
my question is: can i use the cmv early promoter for the zeocin resistance even though this is also the promoter for my insert. i have never seen a plasmid, where insert and resistance gene are under control of the same promoter..

thx for any answer.
dex

In case youre interested, i asked a professor. she said: people think that if 2 promoters of the same kind are on the plasmid they might hinder each other because they need the same factors. so the two promoters are in a competition which might lead to reduced expression of one or both of the products. To avoid such effects you prefere to have different promoters.