title: AID to overcome the limitations of genomic information by introducing somatic DNA alterations.
abstract: The immune system has adopted somatic DNA alterations to overcome the limitations of the genomic information. Activation induced cytidine deaminase (AID) is an essential enzyme to regulate class switch recombination (CSR), somatic hypermutation (SHM) and gene conversion (GC) of the immunoglobulin gene. AID is known to be required for DNA cleavage of S regions in CSR and V regions in SHM. However, its molecular mechanism is a focus of extensive debate. RNA editing hypothesis postulates that AID edits yet unknown mRNA, to generate specific endonucleases for CSR and SHM. By contrast, DNA deamination hypothesis assumes that AID deaminates cytosine in DNA, followed by DNA cleavage by base excision repair enzymes. We summarize the basic knowledge for molecular mechanisms for CSR and SHM and then discuss the importance of AID not only in the immune regulation but also in the genome instability.
authors: Department of Immunology and Genomic Medicine Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors: Tasuku
authors: T
authors: Honjo
authors: Department of Immunology and Genomic Medicine Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors: Masamichi
authors: M
authors: Muramatsu
authors: Department of Immunology and Genomic Medicine Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors: Hitoshi
authors: H
authors: Nagaoka
authors: Department of Immunology and Genomic Medicine Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors: Kazuo
authors: K
authors: Kinoshita
authors: Department of Immunology and Genomic Medicine Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors: Reiko
authors: R
authors: Shinkura
keywords: Activation induced cytidine deaminase; DNA deamination; RNA editing; class switch recombination; genome instability; somatic hypermutation