Forming a chromium-based interstrand DNA crosslink: Implications for carcinogenicity.

Area of Science:

• Environmental Science
• Biochemistry
• Toxicology

Background:

• Chromate reduction generates Cr(III)-DNA lesions, including binary adducts, interstrand crosslinks, and ternary adducts.
• While binary adduct structures are known, interstrand crosslink and ternary adduct structures remain uncharacterized.
• Understanding these structures is crucial for assessing chromate's genotoxicity.

Purpose of the Study:

• To elucidate the structure of Cr(III)-mediated DNA interstrand crosslinks.
• To investigate the binding of Cr(III) to a specific oligonucleotide sequence (5'-CG site).

Main Methods:

• Analysis of Chromium(III) binding to a synthetic oligonucleotide duplex containing a 5'-CG site.
• Structural elucidation of the resulting Cr(III)-DNA complex.

Main Results:

• A novel oxide- or hydroxide-bridged binuclear Cr(III) assembly bridging two DNA strands was identified.
• One Cr(III) ion coordinated to the N-7 atom of a guanine residue.
• The complex formed a hydrogen bond between another guanine and a Cr(III)-bound aquo ligand, without involving the phosphate backbone.

Conclusions:

• The identified Cr-O(H)-Cr bridged complex structure differs significantly from previously reported Cr-induced interstrand crosslinks.
• This suggests that Cr-induced interstrand crosslinks resulting from chromate reduction may possess an organic structure.
• Further research is needed to fully characterize the diverse mechanisms of chromate-DNA interaction.