Intermediates in the ultrafast repair of DNA by DNA photolyase

摘要

It is widely known that ultraviolet (UV)light causes DNA damage. The most commonform of UV lesion found in DNA is the cis-synpyrimidine dimer (CPD) in which adjacentpyrimidines on a DNA strand undergo a 2+2photocycloaddition to generate a cyclobutanering joining the two rings across the 5-and 6-carbon atoms of the pyrimidine ring. Thestructure of a thymidine-thymidine CPD lesionhas been solved most recently by x-raycrystallography for a dodecamer duplex 11. (SeeFigure 1). The 5' thymidine of the CPD lesionhas a longer hydrogen bond distance to itscomplementary adenine (2.4 A) than the 3'thymidine (1.9 A). Base stacking is alsosignificantly more disrupted at the 5' end of theCPD, and this may be the motif that causesmutation or regulation problems that lead todisease or death.