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Book of Abstracts: Albany 2007

category image Albany 2007
Conversation 15
June 19-23 2007

Platinum Anticancer Drug Damage Alters the Rotational Setting of Positioned Nucleosomes

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 in a nucleosome positioning sequence by transferring histones from HeLa-S3 cancer cells onto synthetic DNA duplexes. 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 cross-link faces toward the histone core. Additionally, we determined that cisplatin unwinds nucleosomal DNA globally by approximately 24°. The adduct is located in an area of the nucleosome that contains overwound DNA in undamaged reference nucleosomes. Because most nucleosome positions in vivo are defined by the intrinsic DNA sequence, the capability of cisplatin to influence the structure of these positioned nucleosomes may be of physiological relevance.

Acknowlegement

This work was supported by the NIH grant CA34992 and by a Feodor-Lynen Fellowship to M. O. from the Alexander von Humboldt Foundation, Germany.

Matthias Ober
Stephen J. Lippard*

Department of Chemistry
Massachusetts Institute of Technology
Cambridge, MA, 02139

Phone: +1-617-253-1824
Fax: +1-617-258-8150
Email: lippard@mit.edu