The level and properties of DNA polymerase activity assayable in extracts of avian erythroid cells was studied. The enzyme was detectable in the dividing cells (erythroblasts) of the erythropoietic series and also the immature non-dividing erythrocytes. It could not be assayed in mature erythrocytes. Investigations showed that activity began to decline at the time of the last cell division of the erythroid series. Properties of the enzyme did change in different cell types; however, the changes did not correlate with cessation of DNA synthesis. Some preliminary results on DNA synthesis by isolated nuclei are also reported and these showed that only nuclei from erythroblasts could synthesize DNA in vitro in the absence of primer.
The mutational specificity of DNA polymerase-beta during in vitro DNA synthesis. Production of frameshift, base substitution, and deletion mutations.