Double stable transfection

[Brian Ballard]

In article <mailman.507.1155040575.20007.methods at net.bio.net>,
 <arnaud.garcon at syngenta.com> wrote:

> I've developped several cell lines with two inserts and all that DK said
> makes sense. 
> Invitrogen pBud vector is OK but I thought that their sectable marker
> rZeocin sucks. I know someone from this company reads this list and is
> of an obvious different opinion but there you go.
> I ended up using two linearised plasmids with two orthogonal selection
> markers(ie with different MoA). Then you need to optimised your
> conditions for each in a kind of checker board matrix then your
> selection routine. Hard work at first but works well eventually.
> 
> A.-

I maybe missing something here, but why does everyone suggest 
reoptimising selection conditions for dual transfections - I don't see 
the logic? I have done may dual selections using various combinations of 
blasticidin, G418, zeocin and hygromycin resitance as amrkers and 
although I have had to screen quite a few colonies to get what I want, I 
haven't had to use a matrix of selection conditions. Selection was just 
based on the original kill curves I made for the different antibiotics 
for each cell line transfected. As I said perhaps I'm missing something, 
but why should the kill curves shift when more than one antibiotic is 
being used if each one has a different MOI?

Brian