Inhibitory Effect of Irradiation of DNA with Near Ultraviolet Light in the Presence of 8-Methoxypsoralen on Cleavage by Restriction Endonucleases

Abstract

The pBR322 DNA was irradiated with black light in the presence of 8-methoxypsoralen and digested by various restriction endonucleases including Hin dIII and Rsa I. It was found that for every restriction enzymes examined digestion products specific for pretreated DNA appeared as expected from the inhibition of cleavage presumably due to the formation of corsslinks at the cutting site or within the recognition sequence. Cleavage by Hin dill was affected sensitively by pretreatment of DNA with irradiation in the presence of 8-MOP. The results were discussed in terms of stringency of enzymes to the structural changes of DNA and/or of the unique base sequence favorable to form crosslink.