Alleviation of C⋅C Mismatches in DNA by the Escherichia coli Fpg Protein

Frontiers in Microbiology

Miglė Tomkuvienė¹  Saulius Klimašauskas¹  Peter Ruoff²  Aysha Arshad²  Almaz Nigatu Tesfahun²  Marina Alexeeva²  Prashanna Guragain²  Svein Bjelland³  Arne Klungland⁵ 

[1] Department of Biological DNA Modification, Institute of Biotechnology, Vilnius University, Vilnius, Lithuania;Department of Chemistry, Bioscience and Environmental Technology, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway;Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway;Department of Microbiology, Oslo University Hospital, Oslo, Norway;Department of Molecular Medicine, Life Sciences Center, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway;

关键词: DNA base mismatch;    cytosine:cytosine mismatch;    thymine:thymine mismatch;    base excision repair;    DNA glycosylase;    Escherichia coli Fpg;   

DOI  :  10.3389/fmicb.2021.608839

来源: DOAJ

【 摘 要 】

DNA polymerase III mis-insertion may, where not corrected by its 3′→ 5′ exonuclease or the mismatch repair (MMR) function, result in all possible non-cognate base pairs in DNA generating base substitutions. The most thermodynamically unstable base pair, the cytosine (C)⋅C mismatch, destabilizes adjacent base pairs, is resistant to correction by MMR in Escherichia coli, and its repair mechanism remains elusive. We present here in vitro evidence that C⋅C mismatch can be processed by base excision repair initiated by the E. coli formamidopyrimidine-DNA glycosylase (Fpg) protein. The kcat for C⋅C is, however, 2.5 to 10 times lower than for its primary substrate 8-oxoguanine (oxo8G)⋅C, but approaches those for 5,6-dihydrothymine (dHT)⋅C and thymine glycol (Tg)⋅C. The KM values are all in the same range, which indicates efficient recognition of C⋅C mismatches in DNA. Fpg activity was also exhibited for the thymine (T)⋅T mismatch and for N4- and/or 5-methylated C opposite C or T, Fpg activity being enabled on a broad spectrum of DNA lesions and mismatches by the flexibility of the active site loop. We hypothesize that Fpg plays a role in resolving C⋅C in particular, but also other pyrimidine⋅pyrimidine mismatches, which increases survival at the cost of some mutagenesis.

【 授权许可】

Unknown