Record Details
Covalent binding of the carcinogen benzo(a)pyrene diol epoxide to Xenopus laevis 5S DNA reconstituted into nucleosomes
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Covalent binding of the carcinogen benzo(a)pyrene diol epoxide to Xenopus laevis 5S DNA reconstituted into nucleosomes |
| Names |
Smith, Bettye Lynne, 1961-
(creator) |
| Date Issued | 1992 (iso8601) |
| Note | Access restricted to the OSU Community |
| Abstract | In the nucleus, DNA is complexed with an array of proteins and compacted into chromatin. The basic subunit of chromatin, termed the nucleosome, is composed of 148 base pairs of DNA wrapped around an octamer of the core histones H2A, H2B, H3 and H4. The linker DNA connecting adjacent nucleosomes is associated with histone H1 facilitating further compaction. It has been demonstrated that the dynamic structure of chromatin regulates the expression of genes primarily through nucleosomal positioning. By studying the effects that DNA topology, protein composition, and nucleosome spacing and phasing have on in vitro-assembled chromatin we may begin to understand the mechanisms by which eukaryotic genes are regulated. Because chromatin structure is considered an important regulator in gene expression, the disruption of nucleosomes by the interaction with electrophilic substrates (e.g. carcinogens) could be an important factor in the action of carcinogen binding to DNA resulting in mutagenesis, cell proliferation, and cell toxicity. I have approached this subject by studying the covalent binding of a potent carcinogen, 7r, 8t-dthydroxy- 9t, 10t- oxy- 7, 8, 9, 10-tetrahydrobenzo[a] pyrene (BPDE-I) to nucleosomal and free DNA, using a defined fragment of DNA derived from the 5'-end of the 5S RNA gene of Xenopus laevis. The 430 base pair DNA fragment was prepared from a 5S-DNA-containing plasmid using polymerase chain reaction, end-labeled with ³²P, and reconstituted into nucleosomes by salt-exchange with unlabeled chicken mononucleosomes. Micrococcal nuclease protection experiments demonstrated the formation of two uniquely positioned nucleosomes. BPDE-I modified nucleosomes or free DNA were irradiated with laser light at 355 nm, causing strand breaks at the positions of adducts. Nucleosomal DNA exhibited a marked decrease in the level of binding, suggesting that to a large extent, DNA complexed with nucleosomes is protected from attack by BPDE-I. |
| Genre | Thesis |
| Topic | Benzopyrene -- Toxicity testing |
| Identifier | http://hdl.handle.net/1957/53808 |
