Effect of nucleosome structure on DNA interstrand cross-linking reactions.
Antitumor agents of the nitrogen mustard family and mitomycin C form interstrand cross-links in duplex DNA. To provide information about the cellular mechanism by which these compounds exert their cytotoxic effects, we examined cross-linking of a nucleosomal core particle formed on a fragment of the 5S RNA gene of Xenopus borealis. For the mustards mechlorethamine, chlorambucil, and melphalan, both sites of monoalkylation and interstrand cross-linking were similar in nucleosomal and free DNA. Some small (two- to three- fold) differences in intensity of cross-linking at some sites were apparent. However, these differences did not appear to correlate with rotational or translational positioning. For mitomycin C, cross-linking was inhibited five- to ten-fold at the nucleosomal dyad and showed attenuation of inhibition toward the ends. Furthermore, rotational positioning also appeared to be a factor, with sites facing inward in the nucleosome less accessible for mitomycin cross-linking. None of these agents demonstrated the 10-base pair periodicity exhibited by hydroxyl radical cleavage of nucleosomal DNA.
Millard
J T
JT
Department of Chemistry, Colby College, Waterville, Maine 04901, USA. jtmillar@colby.edu
Spencer
R J
RJ
Hopkins
P B
PB
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000737:chemistry*; D001483:Base Sequence; D002699:Chlorambucil / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry*; D004275:DNA, Ribosomal / Q000737:chemistry*; D008466:Mechlorethamine / Q000737:chemistry; D008558:Melphalan / Q000737:chemistry; D008969:Molecular Sequence Data; D009588:Nitrogen Mustard Compounds / Q000737:chemistry*; D009707:Nucleosomes / Q000737:chemistry*; D012341:RNA, Ribosomal, 5S; D014981:Xenopus
D018906:Antineoplastic Agents, Alkylating; D003432:Cross-Linking Reagents; D004275:DNA, Ribosomal; D009588:Nitrogen Mustard Compounds; D009707:Nucleosomes; D012341:RNA, Ribosomal, 5S; D002699:Chlorambucil; D008466:Mechlorethamine; D008558:Melphalan