Open AccessUncoupling of the recBC ATPase from DNase by DNA Crosslinked with Psoralen
Author(s) -
Alexander E. Karu,
Stuart Linn
Publication year - 1972
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.69.10.2855
Subject(s) - dna , psoralen , ethidium bromide , deoxyribonuclease i , nuclease , biology , recbcd , biochemistry , microbiology and biotechnology , micrococcal nuclease , chemistry , dna repair , histone , nucleosome , base sequence
Exonucleolytic cleavage of DNA by therecBC DNase is accompained by a DNA-dependent ATP hydrolysis that ceases when the DNA that has been digested to a limit. On the other hand, DNA that has been crosslinked by 4,5′,8-trimethylpsoralen in the presence of 360-nm light remains an effective cofactor in the ATPase reaction, but is resistant to digestion by the enzyme. Psoralentreated DNA is degraded by pancreatic DNase, micrococcal nuclease, andEscherichia coli B restriction enzyme, but not byNeurospora crassa nuclease, suggesting that crosslinking did not grossly distort the duplex structure of the DNA. The psoralen-DNA is not a potent inhibitor, but competes with single-stranded DNA from bacteriophage fd for therecBC DNase to roughly the same extent as does normal duplex DNA. DNA treated with psoralen in the dark, exposed to 360-nm light in the absence of psoralen, or treated with the intercalating agents ethidium bromide, 9-aminoacridine, ICR-191, or actinomycin D, responds to the enzyme no differently from untreated DNA. However, DNA crosslinked with mitomycin C or nitrogen mustard behaves similarly to psoralen-treated DNA. The relationship of these findings to models for the function and control of therecBC ATPase and nuclease, and the advantages of psoralen as a DNA crosslinking agent, are discussed.