title: Expression and recruitment of uracil-DNA glycosylase are regulated by E2A during antibody diversification.
abstract: B-lymphocytes can modify their immunoglobulin (Ig) genes to generate specific antibodies with a new isotype and enhanced affinity against an antigen. Activation-induced cytidine deaminase (AID), which is positively regulated by the transcription factor E2A, is the key enzyme that initiates these processes by deaminating cytosine to uracil in Ig genes. Nuclear uracil-DNA glycosylase (UNG2) is subsequently required for uracil processing in the generation of high affinity antibodies of different isotypes. Here we show that the transcription factor E2A binds to the UNG2 promoter and represses UNG2 expression. Inhibition of E2A by binding of Ca(2+)-activated calmodulin alleviates this repression. Furthermore, we demonstrate that UNG2 preferentially accumulates in regions of the Ig heavy chain (IgH) gene containing AID hotspots. Calmodulin inhibition of E2A strongly enhances this UNG2 accumulation, indicating that it is negatively regulated by E2A as well. We show also that over-expression of E2A can suppress class switch recombination. The results suggest that E2A is a key factor in regulating the balance between AID and UNG2, both at expression and Ig targeting levels, to stimulate Ig diversification and suppress normal DNA repair processes.
authors.affiliation: Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, N-7489, Trondheim, Norway; Department of Molecular Biology, Umeå University, 90187, Umeå, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Wallenius
authors.affiliation: Department of Molecular Biology, Umeå University, 90187, Umeå, Sweden.
authors.forename: Jannek
authors.initials: J
authors.lastname: Hauser
authors.affiliation: Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, N-7489, Trondheim, Norway.
authors.forename: Per Arne
authors.initials: PA
authors.lastname: Aas
authors.affiliation: Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, N-7489, Trondheim, Norway.
authors.forename: Antonio
authors.initials: A
authors.lastname: Sarno
authors.affiliation: Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, N-7489, Trondheim, Norway.
authors.forename: Bodil
authors.initials: B
authors.lastname: Kavli
authors.affiliation: Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, N-7489, Trondheim, Norway. Electronic address: hans.krokan@ntnu.no.
authors.forename: Hans E
authors.initials: HE
authors.lastname: Krokan
authors.affiliation: Department of Molecular Biology, Umeå University, 90187, Umeå, Sweden. Electronic address: Thomas.Grundstrom@molbiol.umu.se.
authors.forename: Thomas
authors.initials: T
authors.lastname: Grundström
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D051792:Basic Helix-Loop-Helix Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D002478:Cells, Cultured; D003564:Cytidine Deaminase / Q000276:immunology*; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000276:immunology; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D034741:RNA, Small Interfering; D051981:Uracil-DNA Glycosidase / Q000096:biosynthesis* / Q000235:genetics; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D002147:Calmodulin; D003564:Cytidine Deaminase; D004268:DNA-Binding Proteins; D007143:Immunoglobulin Heavy Chains; D034741:RNA, Small Interfering; D051981:Uracil-DNA Glycosidase; D000098830:AICDA (Activation-Induced Cytidine Deaminase); C075668:Tcf3 protein, mouse
keywords: Antibodies; B cells; Cell differentiation; Gene regulation; Transcription factors