Photochemistry and photobiology of 5-azacytidine: Effect of repair on photostabilization of Escherichia coli

✍ Scribed by Prof. Dr. med. Z. Hradečná; Dr. L. Kittler; G. Löber

• Book ID: 102387461
• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 437 KB
• Volume: 18
• Category: Article
• ISSN: 0233-111X
• DOI: 10.1002/jobm.19780180804

✦ Synopsis

Abstract

The photochemical stability of the anomalous nucleic acid base 5‐azacytidine (z^5^Cyd)^1^) on irradiation at 254 nm is by about one order of magnitude less than that of cytidine (Cyd). Contrary to the photochemical behaviour, incorporation of z^5^Cyd into the nucleic acids of E. coli strains SR 20 (uvr^+^ rec^+^), SR 74 (uvr^+^ rec^−^) and SR 22 (uvr^−^ rec^+^) produced a higher resistance to UV light. Only the SR 73 (uvr^−^ rec^−^) strain was shown to have an increased UV sensitivity. This latter finding is in accord with the photochemical properties of z^5^Cyd. The results led to the conclusion that excision and recombination repair processes contribute to the observable protective effect. The fact that inhibition of excission repair by caffeine or proflavine of the mutant uvr^+^ rec^−^ changes protection into sensitization supports this idea.