3,N4-ethenocytosine, a highly mutagenic adduct, is a primary substrate for Escherichia coli double-stranded uracil-DNA glycosylase and human mismatch-specific thymine-DNA glycosylase

AUTOR(ES)

Saparbaev, Murat

FONTE

The National Academy of Sciences

RESUMO

Exocyclic DNA adducts are generated in cellular DNA by various industrial pollutants such as the carcinogen vinyl chloride and by endogenous products of lipid peroxidation. The etheno derivatives of purine and pyrimidine bases 3,N4-ethenocytosine (ɛC), 1,N6-ethenoadenine (ɛA), N2,3-ethenoguanine, and 1,N2-ethenoguanine cause mutations. The ɛA residues are excised by the human and the Escherichia coli 3-methyladenine-DNA glycosylases (ANPG and AlkA proteins, respectively), but the enzymes repairing ɛC residues have not yet been described. We have identified two homologous proteins present in human cells and E. coli that remove ɛC residues by a DNA glycosylase activity. The human enzyme is an activity of the mismatch-specific thymine-DNA glycosylase (hTDG). The bacterial enzyme is the double-stranded uracil-DNA glycosylase (dsUDG) that is the homologue of the hTDG. In addition to uracil and ɛC-DNA glycosylase activity, the dsUDG protein repairs thymine in a G/T mismatch. The fact that ɛC is recognized and efficiently excised by the E. coli dsUDG and hTDG proteins in vitro suggests that these enzymes may be responsible for the repair of this mutagenic lesion in vivo and be important contributors to genetic stability.

Documentos Relacionados

• Efficient removal of uracil from G.U mispairs by the mismatch-specific thymine DNA glycosylase from HeLa cells.
• Mitochondrial inhibition of uracil-DNA glycosylase is not mutagenic
• Consensus sequences for good and poor removal of uracil from double stranded DNA by uracil-DNA glycosylase.
• Excision of cytosine and thymine from DNA by mutants of human uracil-DNA glycosylase.
• Uracil-DNA glycosylase of thermophilic Thermothrix thiopara.