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Use of oligonucleotides to define the site of interstrand cross-links induced by Adriamycin
1School of Biochemistry, La Trobe University, Bundoora, Victoria, Australia.
Abstract:
It has been known for several years that Adriamycin forms adducts and interstrand cross-links when reacted for long periods of time with bacterial and mammalian DNA in vitro, with the cross-link being restricted to 2 bp elements containing GpC sequences. The self-complementary 20mer deoxyoligonucleotide TA4T4GCA4T4A has been used in this study as a model of the apparent G-G cross-linking site at GpC sequences. The rate of formation of cross-links, as well as the dependence on both Adriamycin and Fe(III) concentration, were similar with this oligonucleotide as compared with calf thymus DNA. The cross-linking was demonstrated on both denaturing and non-denaturing sequencing gels. The half-life of the G-G cross-link was 40 h, consistent with that implied with high molecular weight, heterogeneous sequence DNA. Exonuclease III digests of adducts formed with 20mer deoxyoligonucleotides containing single, central G-G, G-I and I-I potential cross-links revealed that a guanine residue is required at both ends of the cross-link. No cross-linking was observed with a similar oligonucleotide containing only a single central (G.C) bp.
Insights
Adriamycin forms DNA interstrand cross-links at GpC sites, requiring guanine at both ends. This study models Adriamycin-DNA cross-linking using a specific oligonucleotide, confirming guanine
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Adriamycin (doxorubicin) is known to form DNA adducts and interstrand cross-links.
- These cross-links are primarily observed at GpC sequences in both bacterial and mammalian DNA.
- The precise mechanism and sequence requirements for Adriamycin-induced cross-linking require further elucidation.
Purpose of the Study:
- To investigate the role of guanine residues in Adriamycin-induced DNA interstrand cross-linking.
- To characterize the formation and stability of Adriamycin-DNA cross-links using a model oligonucleotide.
- To determine the sequence specificity of Adriamycin cross-linking at GpC sites.
Main Methods:
- Utilized a self-complementary 20-mer deoxyoligonucleotide (TA4T4GCA4T4A) as a model system for GpC sequences.
- Analyzed Adriamycin-Fe(III) cross-linking kinetics and concentration dependence.
- Employed denaturing and non-denaturing sequencing gels to visualize cross-links.
- Performed Exonuclease III digestion assays on modified oligonucleotides.
Main Results:
- Adriamycin-Fe(III) cross-linking rates and dependencies were comparable between the model oligonucleotide and calf thymus DNA.
- The half-life of the G-G cross-link was determined to be approximately 40 hours.
- Exonuclease III digestion revealed that guanine residues are essential at both ends of the cross-link.
- No cross-linking occurred with an oligonucleotide containing a single central G.C base pair.
Conclusions:
- Guanine residues at both ends of a GpC sequence are critical for Adriamycin-induced interstrand cross-linking.
- The 20-mer oligonucleotide model accurately reflects cross-linking behavior observed in larger DNA molecules.
- These findings provide detailed insights into the sequence-specific mechanism of Adriamycin DNA damage.
