title: Genomic uracil homeostasis during normal B cell maturation and loss of this balance during B cell cancer development.
abstract: Activation-induced deaminase (AID) converts DNA cytosines to uracils in immunoglobulin genes, creating antibody diversification. It also causes mutations and translocations that promote cancer. We examined the interplay between uracil creation by AID and its removal by UNG2 glycosylase in splenocytes undergoing maturation and in B cell cancers. The genomic uracil levels remain unchanged in normal stimulated B cells, demonstrating a balance between uracil generation and removal. In stimulated UNG(-/-) cells, uracil levels increase by 11- to 60-fold during the first 3 days. In wild-type B cells, UNG2 gene expression and enzymatic activity rise and fall with AID levels, suggesting that UNG2 expression is coordinated with uracil creation by AID. Remarkably, a murine lymphoma cell line, several human B cell cancer lines, and human B cell tumors expressing AID at high levels have genomic uracils comparable to those seen with stimulated UNG(-/-)splenocytes. However, cancer cells express UNG2 gene at levels similar to or higher than those seen with peripheral B cells and have nuclear uracil excision activity comparable to that seen with stimulated wild-type B cells. We propose that more uracils are created during B cell cancer development than are removed from the genome but that the uracil creation/excision balance is restored during establishment of cell lines, fixing the genomic uracil load at high levels.
authors.affiliation: Department of Chemistry, Wayne State University, Detroit, Michigan, USA.
authors.forename: Sophia
authors.initials: S
authors.lastname: Shalhout
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Dania
authors.initials: D
authors.lastname: Haddad
authors.affiliation: Department of Internal Medicine, Wayne State University School of Medicine, Detroit, Michigan, USA.
authors.forename: Angela
authors.initials: A
authors.lastname: Sosin
authors.affiliation: Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, Michigan, USA.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Holland
authors.affiliation: Department of Internal Medicine, Wayne State University School of Medicine, Detroit, Michigan, USA.
authors.forename: Ayad
authors.initials: A
authors.lastname: Al-Katib
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Alberto
authors.initials: A
authors.lastname: Martin
authors.affiliation: Department of Chemistry, Wayne State University, Detroit, Michigan, USA Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, Michigan, USA axb@chem.wayne.edu.
authors.forename: Ashok S
authors.initials: AS
authors.lastname: Bhagwat
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D003564:Cytidine Deaminase / Q000235:genetics / Q000378:metabolism*; D016678:Genome; D006801:Humans; D008070:Lipopolysaccharides / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008232:Lymphoproliferative Disorders / Q000235:genetics* / Q000378:metabolism; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D014066:Palatine Tonsil / Q000378:metabolism; D013154:Spleen / Q000166:cytology / Q000378:metabolism*; D014498:Uracil / Q000378:metabolism*; D051981:Uracil-DNA Glycosidase / Q000235:genetics / Q000378:metabolism*; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D008070:Lipopolysaccharides; D014498:Uracil; D051981:Uracil-DNA Glycosidase; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase