Polymorphic variant Asp239Tyr of human DNA glycosylase NTHL1 is inactive for removal of a variety of oxidatively-induced DNA base lesions from genomic DNA
Melis Kant, Victoria Quintana, Erdem Coskun, Pawel Jaruga, R. Stephen Lloyd, Joann Sweasy, Miral M. Dizdar
Base excision repair is the major pathway for the repair of oxidatively-induced DNA damage with DNA glycosylases removing modified DNA bases in the first step. Among them, human NTHL1 is specific for excision of several pyrimidine- and purine-derived lesions from DNA. There is evidence that the loss of the function NTHL1 underlies to predisposition to carcinogenesis. A rare single nucleotide polymorphism of the Nthl1 gene leading to the substitution of Asp239 with Tyr within the active site of the protein occurs in the global population, mainly in Europeans, Asians and sub-Saharan Africans. In this work, we overexpressed and purified the variant NTHL1-Asp239Tyr (NTHL1-D239Y). The substrate specificity of this variant and wild-type NTHL1 was investigated using gas chromatography-tandem mass spectrometry with isotope-dilution, and oxidatively-damaged genomic DNA containing multiple pyrimidine- and purine-derived lesions. NTHL1 excised eight DNA base lesions with different efficiencies. In contrast, NTHL1-D239Y exhibited no activity whatsoever for any of these lesions. We also measured the activities of human glycosylases OGG1 and NEIL1, and E. coli glycosylases Nth and Fpg under identical experimental conditions. Different substrate specificities among these DNA glycosylases were observed. When mixed with NTHL1-D239Y, the activity of NTHL1 was not reduced, indicating no competition for binding to the substrates takes place between the two forms of the protein. The results and the inactivity of the variant D239Y toward the major oxidatively-induced DNA lesions points to the importance of the understanding of this variant's role in carcinogenesis and the potential of individual susceptibility to cancer in individuals carrying this variant.
, Quintana, V.
, Coskun, E.
, Jaruga, P.
, Lloyd, R.
, Sweasy, J.
and Dizdar, M.
Polymorphic variant Asp239Tyr of human DNA glycosylase NTHL1 is inactive for removal of a variety of oxidatively-induced DNA base lesions from genomic DNA, ACS Chemical Biology, [online], https://doi.org/10.1016/j.dnarep.2022.103372, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934609
(Accessed February 23, 2024)