This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Larijani, M.
Right arrow Articles by Martin, A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Larijani, M.
Right arrow Articles by Martin, A.

 Previous Article  |  Next Article 

Molecular and Cellular Biology, December 2007, p. 8038-8048, Vol. 27, No. 23
0270-7306/07/$08.00+0     doi:10.1128/MCB.01046-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Single-Stranded DNA Structure and Positional Context of the Target Cytidine Determine the Enzymatic Efficiency of AID{triangledown}

Mani Larijani and Alberto Martin*

Department of Immunology, University of Toronto, Medical Sciences Bldg., Toronto, Canada M5S 1A8

Received 13 June 2007/ Returned for modification 6 August 2007/ Accepted 12 September 2007

Activation-induced cytidine deaminase (AID) initiates antibody diversification processes by deaminating immunoglobulin sequences. Since transcription of target genes is required for deamination in vivo and AID exclusively mutates single-stranded DNA (ssDNA) in vitro, AID has been postulated to mutate transcription bubbles. However, since ssDNA generated by transcription can assume multiple structures, it is unknown which of these are targeted in vivo. Here we examine the enzymatic and binding properties of AID for different DNA structures. We report that AID has minimal activity on stem-loop structures and preferentially deaminates five-nucleotide bubbles. We compared AID activity on cytidines placed at various distances from the single-stranded/double-stranded DNA junction of bubble substrates and found that the optimal target consists of a single-stranded NWRCN motif. We also show that high-affinity binding is required for but does not necessarily lead to efficient deamination. Using nucleotide analogues, we show that AID's WRC preference (W = A or T; R = A or G) involves the recognition of a purine in the R position and that the carbonyl or amino side chains of guanosine negatively influence specificity at the W position. Our results indicate that AID is likely to target short-tract regions of ssDNA produced by transcription elongation and that it requires a fully single-stranded WRC motif.

* Corresponding author. Mailing address: Department of Immunology, University of Toronto, Medical Sciences Bldg. 5265, Toronto, Canada M5S 1A8. Phone: (416) 978-4235. Fax: (416) 978-1938. E-mail: alberto.martin{at}utoronto.ca

{triangledown} Published ahead of print on 24 September 2007.

Molecular and Cellular Biology, December 2007, p. 8038-8048, Vol. 27, No. 23
0270-7306/07/$08.00+0     doi:10.1128/MCB.01046-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»