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Caffeine Inhibition of Postreplication Repair of N-Acetoxy-2-acetylaminofluorene-damaged DNA in Chinese Hamster Cells¹

Department of Human Development, Michigan State University, East Lansing, Michigan 48832 [J. T., P. F.]; Department of Human Genetics, University of Michigan, Ann Arbor, Michigan 48104 [E. H. Y. C.]; and McArdle Laboratory for Cancer Research, University of Wisconsin, Madison, Wisconsin 53706 [J. E. B.]

The effect of caffeine on Chinese hamster cells in vitro, treated with various metabolites and derivatives of 2-acetylaminofluorene, was studied at the molecular level. With the use of an alkaline sucrose gradient centrifugation technique, parental and newly synthesized DNA in control and treated cells were studied in the presence and absence of caffeine. Caffeine synergistically affected only the sedimentation profiles of DNA synthesized in N-acetoxy-2-acetylaminofluorene-treated cells but not in the control cells or in cells treated with the various derivatives of 2-acetylaminofluorene. N-Acetoxy-2-acetylaminofluorene also affected the sedimentation profiles of parental DNA, but caffeine did not influence this effect. At the dose level used, caffeine had no apparent effect on the incorporation of thymidine into DNA in either the control or N-acetoxy-2-acetylaminofluorene-treated cells. These results supplement other reports that suggest that the N-acetoxy-2-acetylaminofluorene lesion in DNA of either human or Chinese hamster cells is repaired similarly to ultraviolet light-induced pyrimidine dimers.

¹ Work was performed at McArdle Laboratory for Cancer Research while J. E. T. was a Career Development Awardee of the Public Health Service (1K4 CA24, 085-01). Research was supported by Grant CA 13048-01 from the National Cancer Institute to J. E. T. and by Departmental Grant CA-07175 to the McArdle Laboratory from the National Cancer Institutes.

Received 1/12/73. Accepted 6/28/73.