Rapid repair kinetics of pyrimidine(6-4)pyrimidone photoproducts in human cells are due to excision rather than conformational change.
AUTOR(ES)
Mitchell, D L
RESUMO
UV-induced pyrimidine(6-4)pyrimidone photoproducts in DNA of mammalian cells are apparently repaired much more rapidly than cyclobutane dimers. Since only immunological assays for (6-4) photoproducts have been sensitive enough for repair measurements, it was possible that these apparently rapid repair kinetics reflected a change in physical conformation of antibody-binding sites, resulting in epitope loss rather than excision. To discriminate between these possibilities, we developed a procedure to photochemically convert (6-4) photoproducts to single-strand breaks in UV-irradiated DNA with a background low enough to permit repair measurements. Analysis of a specific DNA sequence indicated that photoinduced alkali-labile sites (PALS) were induced with the same site-specificity as (6-4) photoproducts. Normal human and xeroderma pigmentosum (XP) variant cells rapidly excised (6-4) photoproducts measured as PALS, but little repair was seen in cells from XP complementation group A. These repair kinetics corresponded to those determined in the same samples by radioimmunoassay of (6-4) photoproducts. Thus we conclude that the rapid repair of (6-4) photoproducts observed in UV-irradiated human cells is not the result of a conformational change resulting in epitope loss, but reflects excision of this photoproduct from DNA.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=330351Documentos Relacionados
- Kinetics of pyrimidine(6-4)pyrimidone photoproduct repair in Escherichia coli.
- The xeroderma pigmentosum group C gene leads to selective repair of cyclobutane pyrimidine dimers rather than 6-4 photoproducts
- Respective roles of pyrimidine dimer and pyrimidine (6-4) pyrimidone photoproducts in UV mutagenesis of simian virus 40 DNA in mammalian cells.
- An ultraviolet light-damaged DNA recognition protein absent in xeroderma pigmentosum group E cells binds selectively to pyrimidine (6-4) pyrimidone photoproducts.
- DNA repair of pyrimidine dimers and 6-4 photoproducts in the ribosomal DNA.