This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Elia, M. C. Articles by Bradley, M. O. Search for Related Content PubMed PubMed Citation Articles by Elia, M. C. Articles by Bradley, M. O.

Influence of Chromatin Structure on the Induction of DNA Double Strand Breaks by Ionizing Radiation

Department of Genetic and Cellular Toxicology, Merck Sharp & Dohme Research Laboratories, West Point, Pennsylvania 19486

Pulsed field gel electrophoresis was used to examine the influence of chromatin structure on the induction of DNA double strand breaks by -irradiation in CHO-WBL cells, nuclei, and a series of protein-depleted chromatin substrates. We developed a method to isolate intact nuclei in agarose plugs that avoids DNA shearing and nucleolytic degradation during sample preparation, and facilitates nuclear protein extraction. Agarose plug-isolated nuclei are extracted with increasing concentrations of NaCl to selectively strip off: (a) nonhistone chromosomal proteins (NHP); (b) NHP and histone H1; (c) NHP, H1, and histone H2A-H2B dimers; or (d) NHP, H1, and H2A-H2B dimers and histone H3-H4 tetramers. Following treatment with up to 40 Gy of -radiation, DNA from each sample is purified and the relative induction of DNA double strand breaks is assayed by asymmetric field inversion gel electrophoresis. At a dose of 20 Gy, removal of nonhistone proteins from nuclei results in a 3-fold increase in DNA double strand breaks, compared to intact CHO cells. Additional stripping of histone H1 results in an incremental increase in double strand break induction, whereas further removal of H2A-H2B dimers yields a greater than 10-fold increase in DNA double strand breaks compared to intact CHO cells. The dose-response profile for this latter sample is similar to that observed for purified DNA. These data indicate that distinct classes of chromosomal proteins afford the DNA with different levels of protection against -ray-induced DNA double strand breaks. Thus, chromatin domains that differ in tertiary structure and protein composition may also differ in their susceptibility to DNA double strand breaks induced by ionizing radiation and, perhaps, other clastogens.

¹ Present address: Genetic Medisyn, 9620 Medical Center Drive, Rockville, MD 20850.

Received 7/29/91. Accepted 12/26/91.

This article has been cited by other articles:

				S. Barker, M. Weinfeld, J. Zheng, L. Li, and D. Murray Identification of Mammalian Proteins Cross-linked to DNA by Ionizing Radiation J. Biol. Chem., October 7, 2005; 280(40): 33826 - 33838. [Abstract] [Full Text] [PDF]

				M.-B. Yin, W. Voigt, A. Panadero, U. Vanhoefer, C. Frank, S. Pajovic, J. Azizkhan, and Y. M. Rustum p53 and WAF1 Are Induced and Rb Protein Is Hypophosphorylated during Cell Growth Inhibition by the Thymidylate Synthase Inhibitor ZD1694 (Tomudex) Mol. Pharmacol., April 1, 1997; 51(4): 630 - 636. [Abstract] [Full Text]