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Platinum anticancer drug damage enforces a particular rotational setting of DNA in nucleosomes.

ABSTRACT: We constructed two site-specifically modified nucleosomes containing an intrastrand cis-{Pt(NH3)2}2+ 1,3-d(GpTpG) cross-link, similar to one formed by the anticancer drugs carboplatin and cisplatin on DNA, and investigated their structures by hydroxyl radical footprinting and exonuclease III digestion. Hydroxyl radical footprinting demonstrated that the presence of the platinum cross-link selects out a specific rotational setting of DNA on the histone octamer core in each of two reconstituted nucleosomes in which the platinum positions differ by half a DNA helical turn. The {Pt(NH3)2}2+ cross-link is situated in a structurally similar location, with the undamaged strand projecting outward, forcing the DNA to adopt opposite rotational settings in its wrapping around the histone octamer in the two nucleosomes. Enzymatic digestion by exonuclease III of the nucleosome substrates revealed that the platinum cross-link affects the translational positioning of the DNA, forcing it into an asymmetric arrangement with respect to the core histone proteins. We suggest that these phasing phenomena may be central to the recognition and processing of platinum-DNA adducts in cancer cells treated with these drugs and possibly may be common to other DNA damaging events.

SUBMITTER: Danford AJ

PROVIDER: S-EPMC1194956 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Cisplatin damage overrides the predefined rotational setting of positioned nucleosomes.

Project description:Cisplatin and carboplatin are used successfully to treat various types of cancer. The drugs target the nucleosomes of cancer cells and form intrastrand DNA cross-links that are located in the major groove. We constructed two site-specifically modified nucleosomes containing defined intrastrand cis-{Pt(NH3)2}(2+) 1,3-d(GpTpG) cross-links. Histones from HeLa-S3 cancer cells were transferred onto synthetic DNA duplexes having nucleosome positioning sequences. The structures of these complexes were investigated by hydroxyl radical footprinting. Employing nucleosome positioning sequences allowed us to quantify the structural deviation induced by the cisplatin adduct. Our experiments demonstrate that a platinum cross-link locally overrides the rotational setting predefined in the nucleosome positioning sequence such that the lesion faces toward the histone core. Identical results were obtained for two DNA duplexes in which the sites of platination differed by approximately half a helical turn. Additionally, we determined that cisplatin unwinds nucleosomal DNA globally by approximately 24 degree. The intrastrand cis-{Pt(NH3)2}(2+) 1,3-d(GpTpG) cross-links are located in an area of the nucleosome that contains locally overwound DNA in undamaged reference nucleosomes. Because most nucleosome positions in vivo are defined by the intrinsic DNA sequence, the ability of cisplatin to influence the structure of these positioned nucleosomes may be of physiological relevance.

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DNA damage detection in nucleosomes involves DNA register shifting.

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Temporal gene regulation by p53 is associated with the rotational setting of its binding sites in nucleosomes.

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