title: AID expression in B-cell lymphomas causes accumulation of genomic uracil and a distinct AID mutational signature.
abstract: The most common mutations in cancer are C to T transitions, but their origin has remained elusive. Recently, mutational signatures of APOBEC-family cytosine deaminases were identified in many common cancers, suggesting off-target deamination of cytosine to uracil as a common mutagenic mechanism. Here we present evidence from mass spectrometric quantitation of deoxyuridine in DNA that shows significantly higher genomic uracil content in B-cell lymphoma cell lines compared to non-lymphoma cancer cell lines and normal circulating lymphocytes. The genomic uracil levels were highly correlated with AID mRNA and protein expression, but not with expression of other APOBECs. Accordingly, AID knockdown significantly reduced genomic uracil content. B-cells stimulated to express endogenous AID and undergo class switch recombination displayed a several-fold increase in total genomic uracil, indicating that B cells may undergo widespread cytosine deamination after stimulation. In line with this, we found that clustered mutations (kataegis) in lymphoma and chronic lymphocytic leukemia predominantly carry AID-hotspot mutational signatures. Moreover, we observed an inverse correlation of genomic uracil with uracil excision activity and expression of the uracil-DNA glycosylases UNG and SMUG1. In conclusion, AID-induced mutagenic U:G mismatches in DNA may be a fundamental and common cause of mutations in B-cell malignancies.
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; Liaison Committee between the Central Norway Regional Health Authority (RHA) and the Norwegian University of Science and Technology (NTNU), Trondheim, Norway; St. Olav's Hospital, Trondheim University Hospital, NO-7006 Trondheim, Norway.
authors.forename: Henrik Sahlin
authors.initials: HS
authors.lastname: Pettersen
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Galashevskaya
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Berit
authors.initials: B
authors.lastname: Doseth
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; The Proteomics and Metabolomics Core Facility (PROMEC) at NTNU, NO-7491 Trondheim, Norway.
authors.forename: Mirta M L
authors.initials: MM
authors.lastname: Sousa
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Antonio
authors.initials: A
authors.lastname: Sarno
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Torkild
authors.initials: T
authors.lastname: Visnes
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Per Arne
authors.initials: PA
authors.lastname: Aas
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Nina-Beate
authors.initials: NB
authors.lastname: Liabakk
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; The Proteomics and Metabolomics Core Facility (PROMEC) at NTNU, NO-7491 Trondheim, Norway.
authors.forename: Geir
authors.initials: G
authors.lastname: Slupphaug
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; Department of Computer and Information Science, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Pål
authors.initials: P
authors.lastname: Sætrom
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway. Electronic address: bodil.kavli@ntnu.no.
authors.forename: Bodil
authors.initials: B
authors.lastname: Kavli
authors.affiliation: Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway. Electronic address: hans.krokan@ntnu.no.
authors.forename: Hans E
authors.initials: HE
authors.lastname: Krokan
mesh_terms: D020137:Base Pair Mismatch; D045744:Cell Line, Tumor; D003564:Cytidine Deaminase / Q000378:metabolism*; D003596:Cytosine / Q000378:metabolism; D004260:DNA Repair; D004273:DNA, Neoplasm / Q000378:metabolism*; D003641:Deamination; D055785:Gene Knockdown Techniques; D006801:Humans; D017578:Immunoglobulin Class Switching; D016393:Lymphoma, B-Cell / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D017354:Point Mutation; D014498:Uracil / Q000378:metabolism*; D051981:Uracil-DNA Glycosidase / Q000378:metabolism; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D004273:DNA, Neoplasm; D014498:Uracil; D003596:Cytosine; C498095:SMUG1 protein, human; D051981:Uracil-DNA Glycosidase; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase
keywords: Activation-induced cytidine deaminase (AID); B-cell lymphoma; Base excision repair; Genomic uracil; Kataegis; Mutational signature