DNA sequence specificity of mitomycin cross-linking

Abstract

Using a gel electrophoresis assay, we show that the target DNA sequence cross-linked by N-methylmitomycin A, its aziridinomitosene, and mitomycin C is CpG, in strong preference over GpC. The yield per CpG site increases as the number of successive CpG sequences increases. Molecular modeling reveals no systematic difference between the energies of mitomycin cross-links at CpG in comparison with GpC. However, the distance between guanine amino groups in CpG sequences is nearly the same as the distance in the cross-linked adduct, whereas the amino group separation at GpC sites is substantially larger in the starting DNA than in the adduct. We suggest that the favorable placement of the second reaction center in CpG greatly accelerates the second step in the cross-linking reaction. As shown by a competition assay, mitomycins bind A-T and G-C sequences noncovalently equally well, even though the only sequence that yields appreciable cross-linking is CpG. N-Methylmitomycin A and its aziridinomitosene are found to be better cross-linking agents than is mitomycin C.

The carbohydrate domain of calicheamicin gamma I1 determines its sequence specificity for DNA cleavage.

“…We assume the following (extremely simplified) scheme, which is analogous to the one that we used for analysis of DNA crosslinking by mitomycin (19):…”

Mitomycin C-induced pairing of heterochromatin reflects initiation of DNA repair and chromatid exchange formation

“…These large C-bands might be particularly prone for crosslinking by MMC. Sequence-specific induction of DNA lesions by MMC is related to a particular order of repeated CpG sequences (Teng et al, 1989;Borowy-Borowski et al, 1990) and is enhanced (two-to fourfold) when the cytosines of these MMC-susceptible sequences are 5-methylated (Johnson et al, 1995;Li et al, 2000;Li et al, 2001). Paracentromeric heterochromatic bands have been reported to contain GC-rich repeats and harbor highly methylated DNA (Miller et al, 1974;Gosden et al, 1975;Meneveri et al, 1993).…”

Cloning and analysis of a locus (mcr) involved in mitomycin C resistance in Streptomyces lavendulae

“…Its unique structural properties and biological activity have motivated numerous studies to determine its cellular target sites and mechanism of action. Complete characterization of MMC (29,30) has been followed by studies examining the basis of its selectivity against mammalian tumor cells and the mechanisms that render mammalian tumor cells MMC resistant (5,14,18,22,26,27). However, the molecular basis for MMC resistance in the producing organism, S. lavendulae, has not been established.…”

“…the hydroquinone (2,12). The second electron transfer is presumed to occur with rapid kinetics (12) and is followed by DNA alkylation and cell death (26,27).…”