ARCHAEBACTERIAL DNA-POLYMERASES TIGHTLY BIND URACIL-CONTAINING DNA

We show that archaebacterial DNA polymerases are strongly inhibited by the presence of small amounts of uracil-containing DNA. Inhibition ap pears to be competitive, with the DNA polymerase exhibiting similar to 6500-fold greater affinity for binding the inhibitor than a DNase I-a ctivated DNA substrate. All six archaebacterial DNA polymerases tested were inhibited, while no eubacterial, eukaryotic, or bacteriophage en zymes showed this effect, Only a small inhibition resulted when uracil was present as the deoxynucleoside triphosphate, dUTP. The rate of DN A synthesis was reduced by similar to 40% when dUTP was used in place of dTTP for archaebacterial DNA polymerases. Furthermore, an incorpora ted dUMP served as a productive 3'-primer terminus for subsequent elon gation. In contrast, the presence of an oligonucleotide containing as little as a single dUrd residue was extremely inhibitory to DNA polyme rase activity on other primer-template DNA.