MUTATIONS INDUCED BY SATURATED AQUEOUS NITRIC-OXIDE IN THE PSP189 SUPF GENE IN HUMAN AD293 AND ESCHERICHIA-COLI MBM7070 CELLS

Nitric oxide is an important bioregulatory agent that may also be an e ndogenous and exogenous human mutagen. In order to study mutations gen erated following exposure of a shuttle vector-borne target gene to nit ric oxide, mutations were induced in the supF gene of the pSP189 shutt le vector by treatment with nitric oxide in aerobic buffered solution followed by replication of the plasmid in either human Ad293 or Escher ichia coli MBM7070 cells. The induced mutation frequency, which increa sed with nitric oxide dose, was 44-fold greater than the spontaneous b ackground in human cells and > 15-fold greater than background in the bacterial cells when a total of 100 mmol of nitric oxide was oxidative ly absorbed/l of pH 7.4 buffer containing the plasmid. The majority of point mutations analysed (61 and 75% for human and E. coli cells resp ectively) were AT-->6GC transitions with GC-->AT transitions (29 and 2 3%) being the next most prevalent. The overall frequencies of the vari ous point mutations seen in the supF gene were similar in the two cell types, although the distribution of hotspots showed differences. The results are consistent with a mutational mechanism initiated by deamin ation of DNA bases.