Both DNA global deformation and repair enzyme contacts mediate flipping of thymine dimer damage.

The photo-induced cis-syn-cyclobutane pyrimidine (CPD) dimer is a frequent DNA lesion. In bacteria photolyases efficiently repair dimers employing a light-driven reaction after flipping out the CPD damage to the active site. How the repair enzyme identifies a damaged site and how the damage is flipped out without external energy is still unclear.

Influence of a cis,syn-cyclobutane pyrimidine dimer damage on DNA conformation studied by molecular dynamics simulations.

The photo-induced formation of cis-syn-cyclobutane pyrimidine dimers (CPD) is a highly mutagenic and cancerogenic DNA lesion. In bacteria photolyases can efficiently reverse the dimer formation employing a light-driven reaction after looping out the CPD damaged bases into the enzyme active site. The exact mechanism how the repair enzyme identifies a damaged site within a large surplus of undamaged DNA is not fully understood.