Recognition of DNA adducts by edited and unedited forms of DNA glycosylase NEIL1

Abstract

Pre-mRNA encoding human NEIL1 undergoes editing by adenosine deaminase ADAR1 that converts a single adenosine to inosine, and this conversion results in an amino acid change of lysine 242 to arginine. Previous investigations of the catalytic efficiencies of the two forms of the enzyme revealed differential release of thymine glycol (ThyGly) from synthetic oligodeoxynucleotides, with the unedited form, NEIL1 K242 being ≈30-fold more efficient than the edited NEIL1 K242R. In contrast, when these enzymes were reacted with oligodeoxynucleotides containing guanidinohydantoin or spiroiminohydantoin, the edited K242R form was ≈3-fold more efficient than the unedited NEIL1. However, no prior studies have investigated the efficiencies of these two forms of NEIL1 on either high-molecular weight DNA containing multiple oxidatively-induced base damages, or oligodeoxynucleotides containing a bulky alkylated formamidopyrimidine. To understand the extent of changes in substrate recognition, γ-irradiated calf thymus DNA was treated with either edited or unedited NEIL1 and the released DNA base lesions analyzed by gas chromatography-tandem mass spectrometry. Of all *

IL-23 Promotes a Coordinated B Cell Germinal Center Program for Class-Switch Recombination to IgG2b in BXD2 Mice

“…Known classical NHEJ players include Ku70 (XRCC6), Ku80 (XRCC5), XRCC4, DNA ligase IV, and DNA-PKcs (29), whereas the nonclassical (or alternative) NHEJ pathway uses XRCC1 and DNA ligase III for DNA end joining (30,31). Other DNA damage/repair gene families, including histone variants H2a and H3a, which encode core histone proteins with substantial variations in their amino and C-terminal regions, DNA polymerase d (POLD) (32,33), and nucleotide excision repair-like (NEIL) (34,35), have been less well studied in CSR. Although AID is considered the master regulator of DNA breaks and NHEJ that enable CSR and we previously showed that a deficiency of IL-17RA in the lupus-prone BXD2 mice affected the expression of AID in vivo and diminished the development of IgG autoantibodies (12), how IL-23 or IL-17 regulate AID-induced NHEJ to promote CSR in immunized or spontaneously autoreactive GC B cells is largely unknown.…”

RNA Editing of the Human DNA Glycosylase NEIL1 Alters Its Removal of 5-Hydroxyuracil Lesions in DNA

“…Indeed, such differences may explain why Gh/Sp and FapyG lesions are processed more efficiently by Ed NEIL1. 28,57 The lesion-specific activity differences of UE versus Ed NEIL1 suggest that cellular responses to oxidative stress will be impacted by the relative amounts of the two isoforms. ADAR1 is induced in T-lymphocytes and macrophages by TNF-α and IFN-γ, 58−60 and therefore, Ed NEIL1 would likely be the predominant form present under conditions of inflammation.…”

“…Moreover, the relative impacts of NEIL1 recoding on lesion sensing, extrusion, and engagement versus enhancing lesion lability would be anticipated to be distinctly different due to the structural features of a given NEIL1 lesion substrate. Indeed, such differences may explain why Gh/Sp and FapyG lesions are processed more efficiently by Ed NEIL1. , …”

DNA Sequence Modulates the Efficiency of NEIL1-Catalyzed Excision of the Aflatoxin B1-Induced Formamidopyrimidine Guanine Adduct

“…NEIL1 is a key human DNA glycosylase/AP lyase responsible for the removal of oxidatively induced lesions [reviewed in ref ]. Its substrates include 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua), − 4,6-diamino-5-formamidopyrimidine (FapyAde), − thymine glycol (ThyGly), − 5-hydroxycytosine (5-OH-Cyt), ,,, and the secondary oxidation products of 8-hydroxyguanine (8-OH-Gua), such as guanidinohydantoin (Gh) and diastereomers of spiroiminodihydantoin (Sp1 and Sp2). ,− ,, Consistent with this broad substrate specificity, NEIL1 also excises methyl- and nitrogen mustard-FapyGua adducts, , psoralen-induced DNA cross-links, , and other lesions. , There are two different forms of intracellular nuclear NEIL1 that arise from the processing of pre-mRNA by adenosine deaminase ADAR1, in which a single adenosine is converted to inosine. This deamination results in an amino acid change in NEIL1 of Lys242 to Arg242 (K242R) and is referred to as the edited form. ,,, Unless otherwise noted, throughout this investigation, we will use the edited form of the enzyme and refer to it as NEIL1.…”