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2-hybrid: Expressionlevel of bait vs prey

Frederik Boernke boernke at ipk-gatersleben.de
Wed Jan 28 10:08:32 EST 1998

Hi all,

I have a question regarding the expression level of the bait protein
vs the expression of target protein. As a bait vector I use the pAS-2
or a derivate in which expression of the GAL4 fusion protein is driven
by the native ADH1 promotor which results in rather high expression.
The AD-library was inserted into pAD-GAL4 (Stratagene) where expression
of the fusion protein is driven by a truncated form of the ADH1 promoter
which results in low expression (not detectable in western). 
The Stratagene manual says about that:"Overexpression of the bait
can result in a phenomenon called "squelching". When squelching occurs, 
ecxess unbound bait protein (not bound to GAL4 UAS) binds target
thereby preventing the target proteins from interacting with the bait 
proteins, which are bound the UAS. Consequently, transcription of 
reporter genes is not activated and interacting proteins are not 

What do you think about this? Shouldn't I combine those two plasmids
different expression level? Or can I disregard that?

Any suggestions will be appreciated.



Frederik Boernke
Research Group of  Molecular Plant Physiologie
Institute for Plant Genetics and Crop Plant Research (IPK)
Corrensstr. 3
06466 Gatersleben
Tel.  039482 -5 321
Fax. 039482 -5 515
e-mail: boernke at ipk-gatersleben.de

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