T4 Endonuclease V has N-glycosylase and apurinic/apyrimidinic
lyase (AP lyase) activities. Ultraviolet (UV) light produces covalent
photoproducts in DNA, the most prevalent being a cis-syn cyclobutane
pyrimidine dimer. T4 Endonuclease V locates and binds to pyrimidine dimers
in dsDNA. The enzyme then cleaves the N-glycosylic bond of the
5´ pyrimidine of the dimer and breaks the phosphodiester bond 3´ to
the resulting abasic site.1
Unit Definition: One unit of T4 Endonuclease V converts 1 µg
of UV-irradiated plasmid DNA from covalently closed circles to nicked
form in 30 minutes at 37°C.
Storage Buffer: 50% glycerol containing 50 mM Tris-HCl (pH 7.5),
100 mM NaCl, 0.1 mM EDTA, 1 mM DTT, and 0.1% Triton® X-100.
Quality Control: T4 Endonuclease V is free of detectable nonspecific
exo- and endonuclease activities and RNase activity.
Figure 1. Mechanism of pyrimidine dimer cleavage by T4 Endonuclease
V. (Adapted with permission from Friedburg, E.C. et al. (1995) DNA
Repair and Mutagenesis, ASM Press.)
Figure 2. Use of T4 Endonuclease V to detect DNA damage caused by
UV exposure. DNA encoding a 1.2-kb DNA fragment was isolated with
(UV+) and without (UV-) exposure to a UV transilluminator
and digested with T4 Endonuclease V (Endo V). Lane 1, 1-kb ladder.