Nucleic Acids Research Advance Access originally published online on February 2, 2009
Nucleic Acids Research 2009 37(6):1854-1867; doi:10.1093/nar/gkp030
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Nucleic Acids Research, 2009, Vol. 37, No. 6 1854-1867
© 2009 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
AID can restrict L1 retrotransposition suggesting a dual role in innate and adaptive immunity
Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA
*To whom correspondence should be addressed. Tel: +1 612 624 0457; Fax: +1 612 625 2163; Email: rsh{at}umn.edu
Received October 22, 2008. Revised January 8, 2009. Accepted January 9, 2009.
Retrotransposons make up over 40% of the mammalian genome. Some copies are still capable of mobilizing and new insertions promote genetic variation. Several members of the APOBEC3 family of DNA cytosine deaminases function to limit the replication of a variety of retroelements, such as the long-terminal repeat (LTR)-containing MusD and Ty1 elements, and that of the non-LTR retrotransposons, L1 and Alu. However, the APOBEC3 genes are limited to mammalian lineages, whereas retrotransposons are far more widespread. This raises the question of what cellular factors control retroelement transposition in species that lack APOBEC3 genes. A strong phylogenetic case can be made that an ancestral activation-induced deaminase (AID)-like gene duplicated and diverged to root the APOBEC3 lineage in mammals. Therefore, we tested the hypothesis that present-day AID proteins possess anti-retroelement activity. We found that AID can inhibit the retrotransposition of L1 through a DNA deamination-independent mechanism. This mechanism may manifest in the cytoplasmic compartment co- or posttranslationally. Together with evidence for AID expression in the ovary, our data combined to suggest that AID has innate immune functions in addition to its integral roles in creating antibody diversity.