The cytidine deaminases AID and APOBEC-1 exhibit distinct functional properties in a novel yeast selectable system

Krause, Kristina; Marcu, Kenneth B; Greeve, Jobst (2006). The cytidine deaminases AID and APOBEC-1 exhibit distinct functional properties in a novel yeast selectable system. Molecular immunology, 43(4), pp. 295-307. Amsterdam: Elsevier 10.1016/j.molimm.2005.05.004

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Activation-induced cytidine deaminase (AID) is indispensable for immunoglobulin maturation by somatic hypermutations and class switch recombination and is supposed to deaminate cytidines in DNA, while its homolog APOBEC-1 edits apolipoprotein (apo) B mRNA by cytidine deamination. We studied the editing activity of APOBEC-1 and AID in yeast using the selectable marker Gal4 linked to its specific inhibitor protein Gal80 via an apo B cassette (Gal4-C) or via the variable region of a mouse immunoglobulin heavy chain gene (Gal4-VH). Expression of APOBEC-1 induced C to U editing in up to 15% of the Gal4-C transcripts, while AID was inactive in this reaction even in the presence of the APOBEC-1 complementation factor. After expression of APOBEC-1 as well as AID approximately 10(-3) of yeast cells survived low stringency selection and expressed beta-galactosidase. Neither AID nor APOBEC-1 mutated the VH sequence of Gal4-VH, and consequently the yeast colonies did not escape high stringent selection. AID, however, induced frequent plasmid recombinations that were only rarely observed with APOBEC-1. In conclusion, AID cannot substitute APOBEC-1 to edit the apo B mRNA, and the expression of AID in yeast is not sufficient for the generation of point mutations in a highly transcribed Gal4-VH sequence. Cofactors for AID induced somatic hypermutations of immunoglobulin variable regions, that are present in B cells and a variety of non-B cells, appear to be missing in yeast. In contrast to APOBEC-1, AID alone does not exhibit an intrinsic specificity for its target sequences.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Department of General Internal Medicine (DAIM) > Clinic of General Internal Medicine
UniBE Contributor:	Greeve, Jobst
ISSN:	0161-5890
ISBN:	15963568
Publisher:	Elsevier
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 14:50
Last Modified:	05 Dec 2022 14:15
Publisher DOI:	10.1016/j.molimm.2005.05.004
PubMed ID:	15963568
Web of Science ID:	000234635900001
URI:	https://boris.unibe.ch/id/eprint/21046 (FactScience: 4923)