Reduced 4,5',8-trimethylpsoralen cross-linking of left-handed Z-DNA stabilized by DNA supercoiling
Z-DNA-forming sequences, (GT)/sub 21/, (GT)/sub 12/ATGT, and (CG)/sub 6/TA(CG)/sub 6/, were cloned into plasmids. These sequences formed left-handed Z-DNA conformations under torsional tension from negative supercoiling of DNA. (/sup 3/H)4,5',8-Trimethylpsoralen, on absorption of 360-nm light, forms monoadducts and interstrand cross-links in DNA that exists in the B-helical conformation. Trimethylpsoralen cross-links were introduced into the potential Z-DNA-forming sequences in relaxed DNA when these sequences existed as B-form DNA. In supercoiled DNA when these sequences existed in the Z conformation, the rate of cross-linking was greatly reduced, and trimethylpsoralen did not form monoadducts appreciably to Z-DNA. As an internal control in these experiments, the rates of cross-linking of the Z-DNA-forming sequences were measured relative to that of an adjacent, cloned sequence that could not adopt a Z conformation. The initial relative rates of cross-linking to Z-DNA-forming sequences were dependent on the superhelical density of the DNA, and the rates were ultimately reduced by factors of 10-15 for Z-DNA in highly supercoiled plasmids. This differential rate of cross-linking provides a novel assay for Z-DNA. Initial application of this assay in vivo suggests that a substantial fraction of (CG)/sub 6/TA(CG)/sub 6/, which existed as Z-DNA in plasmid molecules purified from cells, existed in the B conformation in vivo.
- Research Organization:
- Univ. of Cincinnati College of Medicine, OH
- OSTI ID:
- 6351411
- Journal Information:
- Biochemistry; (United States), Vol. 26:5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DNA
BIOLOGICAL RADIATION EFFECTS
CONFORMATIONAL CHANGES
DNA ADDUCTS
RADIOINDUCTION
CROSS-LINKING
NEAR ULTRAVIOLET RADIATION
PSORALEN
TRITIUM COMPOUNDS
ADDUCTS
ANTICOAGULANTS
BIOLOGICAL EFFECTS
CHEMICAL REACTIONS
COUMARINS
DRUGS
ELECTROMAGNETIC RADIATION
HEMATOLOGIC AGENTS
HETEROCYCLIC COMPOUNDS
LABELLED COMPOUNDS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
POLYMERIZATION
RADIATION EFFECTS
RADIATIONS
ULTRAVIOLET RADIATION
560120* - Radiation Effects on Biochemicals
Cells
& Tissue Culture