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Partial purification of a human DNA glycosylase acting on the cyclic carcinogen adduct 1,N6-ethenodeoxyadenosine

B Rydberg1, Z H Qiu, M K Dosanjh

  • 1Division of Cell and Molecular Biology, Donner Laboratory, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.

Cancer Research
|March 1, 1992
PubMed

Insights

Researchers identified a human DNA glycosylase enzyme that removes 1,N6-ethenoadenine, a DNA adduct formed by a known human carcinogen. This enzyme activity is crucial for DNA repair and preventing mutations.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • DNA Repair Mechanisms

Background:

  • A previously identified Mr35,000 DNA-binding protein selectively recognizes 1,N6-ethenoadenine in double-stranded DNA.
  • 1,N6-ethenoadenine is a cyclic DNA adduct formed by exposure to certain carcinogens.

Purpose of the Study:

  • To investigate the enzymatic activity of the DNA-binding protein that recognizes 1,N6-ethenoadenine.
  • To determine if this protein possesses DNA glycosylase activity for removing the adduct.

Main Methods:

  • Incubation of a defined 25-base double-stranded oligonucleotide containing 1,N6-ethenoadenine with partially purified binding protein from human placenta.
  • Analysis of the reaction products to detect the release of free 1,N6-ethenoadenine base.

Main Results:

  • The partially purified binding protein from human placenta released free 1,N6-ethenoadenine base upon incubation with the modified oligonucleotide.
  • This release is indicative of DNA glycosylase activity, specifically excising the cyclic adduct.

Conclusions:

  • The human DNA-binding protein exhibits DNA glycosylase activity, uniquely excising the 1,N6-ethenoadenine adduct.
  • This enzyme plays a role in the repair of DNA damage caused by human carcinogens.

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