Replication of Initiated Polyriboadenylic Acid by Mammalian Low Molecular Weight Deoxyribonucleic Acid Polymerase

The low molecular weight DNA polymerases isolated from the chromatin and from the cytoplasmic fraction of human, rabbit, bovine, and rat tissues were tested for their ability to use r(pA)n·d(pT)11 as template. The enzyme from all of these tissues can utilize r(pA)n·d(pT)11 as template with almost the same efficiency as d(pA)n·d(pT)11. The polyriboadenylate activity co-purified with the low molecular weight DNA polymerase throughout purification, and showed some relative increase with purification. Replication of r(pA)n· d(pT)11 by the low molecular weight DNA polymerase was extensive, and the product of the replication was a double-stranded hybrid polymer. Analysis of the product of r(pA)n·d(pT)11 replication in the presence of noncomplementary deoxynucleoside triphosphate indicated that the replication is highly accurate, with a misincorporation of deoxycytidylate in polyriboadenylate replication occurring less than 1 in 3 x 105 thymidylates. In the presence of oligothymidylate, the low molecular weight DNA polymerase cannot replicate the heteropolymeric regions of natural RNAs such as chick hemoglobin mRNA or yeast tRNA with polyriboadenylates added at the 3' terminus.