Identification and Characterization of An Intermediate in the Alkali Degradation of (6-4) Photoproduct-containing DNA

Miho Higurashi, Takashi Ohtsuki, Aki Inase, Rika Kusumoto, Chikahide Masutani, Fumio Hanaoka, Shigenori Iwai

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


The (6-4) photoproduct formed by ultraviolet light is known as an alkali-labile DNA lesion. Strand breaks occur at (6-4) photoproducts when UV-irradiated DNA is treated with hot alkali. We have analyzed the degradation reaction of this photoproduct under alkaline conditions using synthetic oligonucleotides. A tetramer, d(GT(6-4)TC), was prepared, and its degradation in 50 mM KOH at 60 °C was monitored by high performance liquid chromatography. A single peak with a UV absorption spectrum similar to that of the starting material was detected after the reaction, and this compound was regarded as an intermediate before the strand break. The formation of this intermediate was compared with intermediates from the degradation of other alkali-labile lesions such as the abasic site, thymine glycol, and 5,6-dihydrothymine. The results strongly suggested that the first step of the alkali degradation of the (6-4) photoproduct was the hydrolysis between the N3 and C4 positions of the 5′-pyrimidine component. Analyses by NMR spectroscopy and mass spectrometry supported the chemical structure of this product. Assays of the complex formation with XPC·HR23B and the translesion synthesis by DNA polymerase η revealed that the biochemical properties are indistinguishable between the intact and hydrolyzed photoproducts.

Original languageEnglish
Pages (from-to)51968-51973
Number of pages6
JournalJournal of Biological Chemistry
Issue number51
Publication statusPublished - Dec 19 2003
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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