Preferential repair incision of cross-links versus monoadducts in psoralen-damaged plasmid DNA by human cell-free extracts

Biochemistry
P CalsouB Salles

Abstract

Upon UVA irradiation psoralens covalently bind to DNA as monoadduct and interstrand crosslink. Psoralen photoadducts are processed via an excision repair reaction that has been reproduced in vitro with transcriptionnally active cell-free extracts. A derived in vitro assay that allows direct quantification of the incised sites has been set up and used to compare the efficiency of the incision reaction on monoadducts and interstrand cross-links. The incision reaction was performed with HeLa cell-free extracts on angelicin or 8-methoxypsoralen (8-MOP)-modified plasmid DNA substrates carrying known amounts of mono- and biadducts, within various relative ratios. In the case of 8-MOP modified plasmids consisting in a mixture of mono- and biadducts on the same DNA molecule, the incision signal was mainly due to the presence of interstrand cross-links. The extent of incision was linear with the number of cross-links up to about 4 cross-links per plasmid and then reached a plateau. The sensitivity of incision defined as the increase of incision by 2-fold over the background level corresponded to about 1 cross-link per plasmid molecule, and about 7% of the total cross-links were repaired under our assay conditions. The incision activity ...Continue Reading

References

Jul 7, 1995·The Journal of Biological Chemistry·A Sancar
May 20, 1993·Journal of Molecular Biology·D E SzymkowskiR D Wood

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Citations

Dec 24, 2013·Journal of Photochemistry and Photobiology. B, Biology·Emanuelle B F SilvaJosé P Siqueira-Júnior
Apr 25, 2002·Proceedings of the National Academy of Sciences of the United States of America·Karen M VasquezPeter M Glazer
Oct 10, 1997·FEBS Letters·F CoudoréB Salles
Jul 27, 2001·Journal of the American Chemical Society·D M NollP S Miller

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