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Genomics II: Bacteria, Viruses and Metabolic Pathways
Genomics II: Bacteria, Viruses and Metabolic Pathways
iConcept Press

Chapter 5

Genomics II: Bacteria, Viruses and Metabolic Pathways

Intrinsic Immunity by APOBEC Family of Cytidine Deaminases against Retrotransposons

by Atsushi Koito

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Mammalian cytidine deaminases APOBECs, which can insert mutations into DNA and/or RNA as a result of their ability to deaminate cytidine (C) to uridine (U), originated from the zinc-dependent deaminase superfamily at the beginning of vertebrate radiation and further expanded in mammals. The ability of mammalian cytidine deaminases encoded by the APOBEC3 genes to restrict a broad number of exogenous pathogens, such as exogenous retroviruses and the mobility of endogenous retroelements, such as endogenous retroviruses, long-interspersed nuclear element (LINE) and short-interspersed nuclear element (SINE) is well established. Furthermore, APOBEC1 from a variety of mammalian species, which mediates the C-to-U deamination of apolipoprotein B mRNA, a protein involved in lipid transport, also has a role in controlling mobile elements. A large portion of the mammalian genome is derived from ancient transposable elements. Retroelements, transported by an intracellular copy-and-paste process involving an RNA intermediate, constitute the majority of these mobile genetic elements. Endogenous retroviruses are long terminal repeat (LTR)-type retroelements that account for ~10% of human and murine genomic DNA. Non-LTR members are present in extremely high copy numbers, with ~40% of the human and murine genomes consisting of LINE. These LINE elements modify mammalian genomes not only through insertions but also by the indirect replication of nonautonomous retrotransposons such as SINE. As expected, vertebrate intrinsic immunity has evolved to support a balance between retroelement insertions that confer beneficial genetic diversity and those that cause deleterious gene disruptions. This review discusses the current understanding of the mechanism of action of APOBEC cytidine deaminases and their role in controlling retrotransposons.

Author Details

Atsushi Koito
Department of Retrovirology and Self-Defense, Faculty of Life Sciences, Kumamoto University, Japan, Japan


Atsushi Koito. Intrinsic Immunity by APOBEC Family of Cytidine Deaminases against Retrotransposons. In Genomics II: Bacteria, Viruses and Metabolic Pathways. ISBN:978-1-480254-145. iConcept Press. 0000.