The base excision repair pathway

DNA glycosylases in the base excision repair of DNA

“…Deletion of amino acids from the Cterminal and N-terminal ends of the human protein resulted in a core enzyme of 248 amino acids that had lost TDG activity but retained double-strand-specific UDG activity. Interestingly, homologues of this core enzyme are present in bacteria as well as in insect cells, and it thus appears to be an ancient enzyme [91]. It may be subservient to the catalytically more efficient form of UDG present in most organisms, but may constitute a first-line defence against the effects of cytosine deamination in insects.…”

“…In contrast, AlkA, the other E. coli enzyme, has the broadest substrate specificity of all known DNA glycosylases. It is the only alkylbase-DNA glycosylase known to remove both damaged purines and pyrimidines [91]. AlkA is also 10-20-fold more efficient than Tag in the removal of 3-meA from single-stranded DNA [136].…”

“…AlkA removes all adducts caused by simple monofunctional alkylating agents, except those repaired by the alkyltransferase Ada. AlkA substrates include 3-meA, 3-meG, 7-meG, 7-meA, O#-alkylcytosine and O#-alkylthymine [91]. Not only are these substrates different in the sense that they represent pyrimidines and purines but, in addition, the methyl group of 7-meG protrudes into the major groove, whereas the other alkyl groups protrude into the minor groove.…”

UV‐B‐ and oxidative stress‐induced increase in nicotinamide and trigonelline and inhibition of defensive metabolism induction by poly(ADP‐ribose)polymerase inhibitor in plant tissue

“…In line with the results by Green and Fluhr [32] we suggest that UV-B exposure in plants may cause increased levels of reactive oxygen species. Oxidative stress may cause DNA damage that is repaired by base excision repair [33], which in animal cells is considered to be associated with PADPRP activity [34]. However, stimulation of PADPRP activity did not seem to occur in response to UV-C exposure in animal cell systems [34].…”

Analysis of DNA Binding and Nucleotide Flipping Kinetics Using Two-Color Two-Photon Fluorescence Lifetime Imaging Microscopy

“…Specifically, an AP endonuclease cleaves the DNA backbone, a deoxyribophosphodiesterase removes the remaining ribosyl sugar from the 5' phosphate and a DNA polymerase and ligase fill and seal the gap. 11 UNG, like many DNA glycosylases, exploits the structural transition known as nucleotide flipping to gain access to the interior of the DNA helix and catalyze the removal of the unwanted base. 12 Despite being discovered two decades ago, 13 the precise molecular mechanism that underlies nucleotide flipping remains unclear.…”