DNA Polymerase β from Brain Neurons Is a Repair Enzyme

Abstract

DNA polymerase β was isolated from rat cortex neurons and characterised. Its properties were strikingly similar to those of other mammalian β‐polymerases. In adult rats, this was the major DNA polymerase occurring in neuronal nuclei, which contained no α‐polymerase, 99.2%β‐polymerase and only 0.8%γ‐polymerase. Isolated neuronal nuclei of this developmental stage were shown to perform ultraviolet‐induced repair DNA synthesis in vitro. Since β‐polymerase was virtually the exclusive DNA polymerase in these nuclei it was concluded that the β enzyme was responsible for the observed DNA repair. This was further substantiated by demonstrating a virtually complete suppression of DNA repair in irradiated nuclei by 2′,3′‐dideoxyribosylthymine 5′‐triphosphate (d2TTP), a potent β‐polymerase inhibitor. However, the presence of minute amounts of γ‐polymerase in neuronal nuclei and its susceptibility to d2TTP did not allow one to rule out an ancillary role of DNA polymerase γ in DNA repair. In view of the similarity of the neuronal DNA polymerase β with all other mammalian β‐polymerases it may be speculated that the ability to perform repair DNA synthesis is not unique to the neuronal enzyme but is a general function of all β‐polymerases. Copyright © 1979, Wiley Blackwell. All rights reserved