calicheamicin-gamma(1)i and hydrazine

Bistranded DNA damage produced by the enediyne antitumor antibiotic calicheamicin (CAL) was examined in plasmid DNA and in a model site for CAL-mediated DNA damage containing the sequence AGGA.TCCT. CAL was observed to produce bistranded DNA damage to the virtual exclusion of single-strand (SS) lesions. Without expression of drug-induced abasic sites as strand breaks, CAL activated by 10 mM glutathione produced equal numbers of DS and SS breaks in plasmid DNA. However, cleavage of drug-induced abasic sites with hydrazine and putrescine resulted in a dramatic increase in the appearance of bistranded damage, with ratios of DS to SS breaks of approximately 6:1 and approximately 24:1, respectively. A similar bias for DS lesions was noted in CAL-mediated damage in the AGGA.TCCT model sequence, in which evidence for a 4'-hydroxylated abasic site was observed on the AGGA strand. These model DNA systems revealed three important features of the bistranded damage produced by CAL. First, the major lesion produced by CAL is a bistranded lesion consisting of an abasic site on one strand and a direct strand break on the other. Second, 3'-phosphoglycolate residues resulting from CAL-induced C4'-hydrogen abstraction at the C of AGGATC were restricted to bistranded lesions. This unusual behavior of the C4'-chemistry of both CAL and the related neocarzinostatin (NCS) is consistent with an intermediate in the partitioning that is dependent on bistranded lesions. Finally, 4-hydroxythiophenol activated CAL to produce a ratio of DS to SS lesions of approximately 10:1, as opposed to the approximately 1:30 ratio noted previously for NCS.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Aminoglycosides; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Base Sequence; Binding Sites; DNA; DNA Damage; DNA, Single-Stranded; Enediynes; Glutathione; Hydrazines; Molecular Sequence Data; Plasmids; Putrescine

A new macromolecular antitumor antibiotic, C-1027, shows potent cytotoxic effects and DNA cutting activity. The DNA cleaving properties of C-1027 are compared with those of other enediyne compounds such as neocarzinostatin, esperamicin A1, and calicheamicin gamma 1. Even in the absence of thiols or reductants, the antibiotic C-1027 has high DNA breakage ability. Of special interest is the fact that C-1027 causes strand breaks two base pairs apart at specific sites such as 5'-TAT/3'-ATA and 5'-AGA/3'-TCT (cleavage sites in italics) in the two strands. This novel double-stranded cleavage fashion is different from that of calicheamicin gamma 1, which is found to have a 3-bp separation between cleavage sites on the two strands. The asymmetric cleavage pattern to the 3'-side and a competitive experiment with distamycin A reveal minor-groove interaction of double-helical DNA with C-1027. This antibiotic appears to oxidize DNA through hydrogen abstraction predominantly at the C-4' carbon of deoxyribose. The activation mechanism of C-1027, which contains an enediyne chromophore of the esperamicin/calicheamicin type, has been proposed.

Topics: Aminoglycosides; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Base Sequence; Binding Sites; DNA; DNA Damage; DNA, Superhelical; Enediynes; Hydrazines; Molecular Sequence Data; Proteins; Zinostatin