AN APHIDICOLIN-RESISTANT MUTANT OF CHINESE-HAMSTER OVARY CELL WITH ALTERED DNA-POLYMERASE AND 3'-EXONUCLEASE ACTIVITIES

A comparison was made of partially purified DNA polymerases alpha, del ta, epsilon and from normal Chinese hamster ovary cells and mutant cel ls (JK3-1-2A) resistant to aphidicolin, araA, and araC. In vitro the p ol alpha from the mutant cells (1) was resistant to aphidicolin and ar aCTP but was sensitive to araATP, (2) showed a 1.6 to 2.6-fold reduced specific activity, and (3) was more sensitive to carbonyldiphosphonat e, DMSO and SJK 287-38 anti-pol alpha antibody inhibition, but was les s sensitive to alkylphenyl nucleotide analogs BuPdGTP and BuAdATP. On the other hand, pol delta and pol epsilon of the mutant cells did not show increased aphidicolin-resistance but differed from the wild type enzymes with regard to their 3' exonuclease activity. The 3' exonuclea se/DNA polymerase activity ratio was increased 6-fold for pol delta an d 3.3-fold for pol epsilon for enzymes from the mutant cells in compar ison to wild type values. It is suggested that these altered propertie s of the DNA polymerases of the a-family are responsible for in vivo a phidicolin resistance of the mutant cells. The higher 3' exonuclease a ctivity may explain the observed antimutator phenotype of this cell li ne. In view of the proficient 3' exonuclease activities of the DNA pol delta and epsilon, the present aph(r) mutant is unique among all mamm alian DNA polymerase mutants.