Inhibition of restriction enzyme cleavage of DNA modified with 7-deaza-dGTP

DNA templates containing G+C rich regions or stable secondary structures can potentially pose problems for polymerase chain reaction amplification. Incorporation of the structure destabilizing analogue, 7-deaza-dGTP into the polymerase chain reaction reaction allows successful amplification of such template sequences. It has been reported that when 7-deaza-dGTP is substituted for dGTP in a DNA-fragment, the cleavage rate by the restriction enzyme EcoRI is reduced. We find that EcoRI as well as other commonly used restriction enzymes will not cut DNA containing 7-deaza-dGTP when it is incorporated into polymerase chain reaction product.