title: Base substitution mutagenesis by terminal transferase: its role in somatic mutagenesis.
abstract: We have addressed the possibility of terminal transferase involvement in somatic mutagenesis and the creation of N-region diversity, by measuring the ability of TdT to enhance single-base substitution mutagenesis during in vitro DNA synthesis. Using 3 independent assays we find that terminal transferase produces only a small increase in base-substitution mutagenesis when assayed in the presence of DNA polymerase-beta. In the presence of either polymerase-alpha or E. coli polymerase-I, however, no detectable increase in TdT-induced mutagenesis is seen. Furthermore, in an assay capable of detecting a variety of mutational events, terminal transferase primarily produces complex addition/deletion mutations, as well as a few multiple, tightly-clustered, single-base mutations. We conclude that the majority of the scattered single-base changes that occur during antibody gene differentiation are not catalyzed by terminal transferase, but instead result from another error-prone DNA synthetic process (possibly utilizing DNA polymerase-beta).
mesh_terms: D010584:Bacteriophage phi X 174 / Q000235:genetics; D001483:Base Sequence; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism*; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004256:DNA Polymerase I / Q000378:metabolism; D009152:Mutagenicity Tests; D009154:Mutation; D011067:Poly dA-dT / Q000378:metabolism; D013698:Templates, Genetic
chemical_list: D011067:Poly dA-dT; D004254:DNA Nucleotidyltransferases; D004253:DNA Nucleotidylexotransferase; D004256:DNA Polymerase I