Preferential insert orientation

[Tim Buss]

Re: Preferential insert orientation

I agree with Peter. This promoter is 'leaky' and there will be a low
level of expression even in the un-induced state. If your protein is at
all toxic to the cell you will tend to only get clones in the reverse
orientation.
I work with immunoglobulins and try to avoid using vectors of this type
for this very reason. 

Consider using a vector with a different promoter.