Co-fractionation of an endonuclease activity during the purification of DNA polymerase-alpha from regenerating rat liver. Properties and separation from DNA polymerase.

The presence of endonuclease activity associated with DNA polymerase was detected during the purification of high-molecular-weight DNA polymerase-alpha from regenerating rat liver by the use of a highly sensitive test. This endonuclease activity co-fractionated with DNA polymerase in a great variety of purification procedures involving ion-exchange chromatographies or molecular weight fractionation, but was further completely separated from DNA polymerase activity by using affinity chromatography on DNA-cellulose. The endonuclease acted on native or denatured DNA by introducing single-strand nicks in the DNA molecules; its enzymatic properties indicate that it could act in polymerisation conditions in vitro.