Patra, Amritraj [Vanderbilt Univ., Nashville, TN (United States); Harp, Joel [Vanderbilt Univ., Nashville, TN (United States); Pallan, Pradeep S. [Vanderbilt Univ., Nashville, TN (United States); Zhao, Linlin [Vanderbilt Univ., Nashville, TN (United States); Abramov, Mikhail [Rega Inst. for Medical Research (Belgium); Herdewijn, Piet [Rega Inst. for Medical Research (Belgium); Univ. of Evry-Val-d' Essonne (France); Egli, Martin [Vanderbilt Univ., Nashville, TN (United States)
The thymine analog 5-chlorouridine, first reported in the 1950s as anti-tumor agent, is known as an effective mutagen, clastogen and toxicant as well as an effective inducer of sister-chromatid exchange. Recently, the first microorganism with a chemically different genome was reported; the selected Escherichia coli strain relies on the four building blocks 5-chloro-2'-deoxyuridine (ClU), A, C and G instead of the standard T, A, C, G alphabet [Marlière,P., Patrouix,J., Döring,V., Herdewijn,P., Tricot,S., Cruveiller,S., Bouzon,M. and Mutzel,R. (2011) Chemical evolution of a bacterium’s genome. Angew. Chem. Int. Ed., 50, 7109–7114]. The residual fraction of T in the DNA of adapted bacteria was <2% and the switch from T to ClU was accompanied by a massive number of mutations, including >1500 A to G or G to A transitions in a culture. The former is most likely due to wobble base pairing between ClU and G, which may be more common for ClU than T. To identify potential changes in the geometries of base pairs and duplexes as a result of replacement of T by ClU, we determined four crystal structures of a B-form DNA dodecamer duplex containing ClU:A or ClU:G base pairs. The structures reveal nearly identical geometries of these pairs compared with T:A or T:G, respectively, and no consequences for stability and cleavage by an endonuclease (EcoRI). The lack of significant changes in the geometry of ClU:A and ClU:G base pairs relative to the corresponding native pairs is consistent with the sustained unlimited self-reproduction of E. coli strains with virtually complete T→ClU genome substitution.
Bender, Matthias; Mouritsen, Henrik
Summary The biosynthetic precursor of redox cofactor F420, 7,8-didemethyl-8-hydroxy-5-deazariboflavin, was prepared in four steps from 6-chlorouracil, 2-chloro-4-hydroxybenzaldehyde and bis-isopropylidene protected D-ribose. The latter aldehyde was transformed to the corresponding protected ribitylamine via the oxime, which was submitted to reduction with LiAlH4. Key advantage compared to previous syntheses is the utilization of a polyol-protective group which allowed the chromatographic purification of a key-intermediate product providing the target compound with high purity. PMID:27340481
The SOS chromotest was applied for the detection of antimutagens. To raise SOS induction, the bacteria were treated with the mutagens, UV, 4-nitroquinoline N-oxide (4NQO), N-methyl-N'-nitro-N-nitroso-guanidine (MNNG), or benzo[a]pyrene (B[a]p). The inhibitory effects of L-ascorbic acid, glutathione, vanillin,5-fluorouracil (5-FU), 5-chlorouracil (5-CU), cobaltous chloride, sodium selenite and sodium arsenite, which are known as antimutagens, were investigated with their addition either simultaneously or post treatment time. In became clear that the SOS chromotest was very useful for the detection of antimutagens