RNA-editing cytidine deaminase Apobec-1 is unable to induce somatic hypermutation in mammalian cells.

Eto, Tomonori; Kinoshita, Kazuo; Yoshikawa, Kiyotsugu; Muramatsu, Masamichi; Honjo, Tasuku · Proc Natl Acad Sci U S A · 2003

basic_science · Level V

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Abstract

Antibody diversification by somatic hypermutation, gene conversion, and class switch recombination is completely dependent on activation-induced cytidine deaminase (AID). A recent report showing induction of DNA mutations in Escherichia coli by overexpression of AID, Apobec-1, and related members of the RNA-editing cytidine deaminase family suggested that they may directly modify deoxycytidine in DNA in mammalian cells (DNA-editing model). We therefore examined whether Apobec-1 bona fide RNA-editing enzyme could show somatic hypermutation and class switching activities in murine B lymphocytes and fibroblasts. Unlike AID, Apobec-1 was unable to induce somatic hypermutation or class switching. The results force a reevaluation of the physiological significance of the DNA deaminase activities of AID and Apobec-1 in E. coli and in vitro.

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