2-hybrid problem

[Nathalie CUEILLE]

Hello everybody

I am a french PhD student (CNRS, Montpellier, France) seeking for 
some help
with my saccharomyces yeast. (e-mail at 73373.1544 at compuserve.com

I have screened a Xenopus cDNA bank (dihybrid technique) to find 
partners
to my bait

I have found 9 clones giving the following phenotype His+/Lac+

After segregation of the clones followed by amplification of the 
cDNA (PCR)
and transformation in E.coli HB101 to eliminate the bait I tried 
to test
the specificity of the interaction by backtransforming these 
clones
with my bait or with RAS.
But I lost in this backtransformation the phenotype Lac+/His+ in 
both cases
though my witness reacts well
what can I do to clear up this mystery?
How can I explain the loss of this phenotype?
How can I test the specificity? thank you -- Nathalie CUEILLE