Key points are not available for this paper at this time.
The bleomycins, a family of glycopeptides with antineoplastic activity, bind to DNA and cause strand-scission in a reaction requiring Fe(I1) and oxygen.Strandscission is accompanied by the simultaneous release of free bases and four low molecular weight compounds that react with 2-thiobarbituric acid to form chromophores absorbing maximally at 532 nm.The structure of these four products was elucidated as follows: formic acid hydrolysis released thymine, cytosine, adenine, and guanine, respectively; treatment of each compound with phenylhydrazine yielded 1-phenylpyrazole.The adenine-containing compound was reduced with sodium borohydride and the trimethylsilyl derivative was prepared.High resolution mass spectrometry of this derivative revealed silylated 3-(adenin-B'-y1)-2-propen-1-01, consistent with formulation of the original compound as 3-(adenin-9'-~1)-2-propenal.The reaction product containing thymine was similarly shown to be 3-(thymin-l'-yl)-2-propenal.The 3-substituted propenal structures proposed were confirmed by chemical synthesis.Oligonucleotides, produced by bleomycin-induced strand-scission, were found to contain glycolic acid residues esterified through the hydroxyl group to the 3'-phosphate termini.We conclude that the primary reaction products resulting from bleomycin-induced strand-scission of DNA have a common structure: Base-CH=CH-CHO.These observations are consistent with a reaction mechanism initiated by free radical abstraction of the C-4' proton of deoxyribose and leading to oxidative cleavage of the (C-3')-(C-43 bond.DNA, isolated from bleomycin-treated cells, is known to be degraded (1-7), an effect which is presumed to be responsible for the chemotherapeutic properties of this family of antibiotics.Bleomycin creates single-and double-stranded breaks in purified preparations of DNA (1, 3-6, 8-19), strand-scission occurring preferentially at guanine-pyrimidine (5' + 3') base sequences (20,21).Products of the reaction between bleomycin and DNA include free bases, oligonucleotides, and several compounds which form chromophores with TBA' (9-11, 18,
Giloni et al. (Sat,) studied this question.