Survival of apurinic SV40 DNA in the d-complementation group of xeroderma pigmentosum.

The survival of depurinated Form I SV40 DNA was studied in normal human fibroblasts and in D-complementation Xeroderma pigmentosum (XP) fibroblasts. Survival was measured with an infective center assay. Heat-acid and methyl methanesulfonate (MMS) were used as depurinating agents. After 3 hrs of depurination by heat--acid treatment, infectivity in normal cells was less than 15% of the controls compared to more than 50% for the XP D cell strains. Similar results were obtained with MMS-treated DNA. These results are contrary to expectation since apurinic endonuclease activity, which is presumed to be involved in the repair of apurinic sites, is much lower in XP D cell strains than in normal cell strains. Our results indicate that another mechanism for the repair of apurinic sites could exist.

Effect of putative deoxyribonucleic acid inhibitors on macromolecular synthesis in Saccharomyces cerevisiae.

The effects of inhibitors of bacterial deoxyribonucleic acid (DNA) synthesis upon logarithmically growing cultures of Saccharomyces cerevisiae were investigated. Cell division, ribonucleic acid (RNA) synthesis, and DNA synthesis were measured after addition of nalidixic acid, fluorodeoxyuridine, or phenethyl alcohol to cultures of yeast growing in defined and complex media. Both nalidixic acid and fluorodeoxyuridine had only temporary effects on nucleic acid synthesis in cultures growing in defined medium, and little or no observable effect on cultures growing in complex medium. Neither compound inhibited colony formation on complex solid medium, although growth was slow on defined solid medium. Phenethyl alcohol caused complete inhibition of DNA synthesis, RNA synthesis, and cell division in cultures growing in defined medium. In cultures growing in complex medium, RNA synthesis and cell division were inhibited to a lesser extent. A slight increase in DNA was observed in the presence of the inhibitor.