Properties of two forms of DNA polymerase .delta. from calf thymus

Publisher Website
Google Scholar
Abstract
Purified calf thymus DNA polymerases .delta. I and II each have an associated 3'' to 5'' exonuclease but otherwise resemble DNA polymerase .alpha. in size, biochemical kinetic parameters, and the presence of DNA primase [Crute, J. J., Wahl, A. F., and Bambara, R. A. (1986) Biochemistry 25, 26-36]. Here we demonstrate a functional association of polymerase and exonuclease with each .delta. form. Furthermore, we show that the exonuclease can be dissociated from DNA polymerase .delta. I but does not appear to be removable from DNA polymerase .delta. II. Polymerases .delta. I, .delta. II, and .alpha. are equally sensitive to the inhibitor amphidicolin, suggesting a similarity in active site structure. In comparison with DNA polymerase .alpha. and .delta. II, DNA polymerase .delta. I has intermediate sensitivity to 2-(p-n-butylanilino)-2''-deoxyadenosine 5''-triphosphate (BuAdATP) or N2-(p-n-butylphenyl)-2''-deoxyguanosine 5''-triphosphate (BuPdGTP). The activity of the DNA primase of the .delta. II enzyme is insensitive to BuAdATP whereas 1.0 .mu.M of this inhibitor will decrease the activity of the DNA primase of the .alpha. and .delta. I enzymes approximately 50%. Two monoclonal antibodies that potently inhibit DNA polymerase .alpha. are only slightly inhibitory to DNA polymerase .delta. I and are ineffective at inhibiting DNA polymerase .delta. II. DNA polymerase .delta. II had been previously found to be nearly inactive on nuclease-treated calf thymus DNA, relative to its activity on homopolymeric DNA. We find that addition of purified calf histone proteins or spermidine can greatly enhance synthesis by this enzyme on activated calf DNA.