cDNA cloning

[Dom Spinella]

> We have been trying to clone cDNA into either the T7 Select vector or 
> Stratagene's Lambda Zap vector. Regardless of the cDNA or the 
> adapters that we use, we consistantly only clone adapters and no 
> cDNA. We have used several types of column chromatography and NH4OAC 
> precipitations to try and clean the free adapters from our cDNA. 
> Even when we use our column chromatography and select fractions 
> that should contain only large DNA (>800bp), we will still only get 
> free adapters cloning. Has anyone else experienced this problem and 
> if so....how do you effectively get rid of all of those adapters?

I've always used a 1% agarose gel to size-select cDNA.  Column
chromatography (as you observed) just doesn't have the resolution to
completely remove the adaptors -- and (also as you observed) they clone
with very high efficiency. Just isolate the cDNA smear above ~600 bp. 
This has always worked great for me.  Good luck.
-Dom Spinella

PS  You might also consider non-palindromic BstX1 adaptors.