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Steven Loechel frosty at biobase.dk
Tue Nov 7 05:07:41 EST 1995

David L. Haviland, Ph.D. (haviland at KIDS.WUSTL.EDU) wrote:

: Quite a while back there was a discussion about pCDNA3 vector.  There was 
: a rumor that a cryptic E. coli promoter existed at or near the HindIII 
: site of the polylinker.  Does anyone have any information to confirm or 
: deny this?

I made a posting many moons ago about this. Perhaps that's what you're
referring to.  I was clearly getting enough fortuitous expression in
E. coli, that there were toxicity problems with a number of the ORFs
I was expressing, when they included a signal sequence for secretion.
I solved the problem in my particular case by sticking an E. coli 
transcriptional terminator immediately upstream of the polylinker. 
That eliminated the toxicity in E. coli, and had no effect on eukaryotic
I got the standard response from Invitrogen that one normally gets 
when one calls any Tech Service Department about problems of this
nature. "Never had a problem with it, nobody's ever complained,
we'll look into the matter."  Perhaps they actually have looked into
the matter by this time. 


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