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Journal of Virology, December 2009, p. 12611-12621, Vol. 83, No. 23
0022-538X/09/$08.00+0 doi:10.1128/JVI.01491-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Functional Analysis and Structural Modeling of Human APOBEC3G Reveal the Role of Evolutionarily Conserved Elements in the Inhibition of Human Immunodeficiency Virus Type 1 Infection and Alu Transposition
,
Yannick Bulliard,1
Priscilla Turelli,1
Ute F. Röhrig,2,3
Vincent Zoete,2
Bastien Mangeat,1,
Olivier Michielin,2,3,4 and
Didier Trono1*
School of Life Sciences and Frontiers-in-Genetics National Center of Competence in Research, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland,1 Swiss Institute of Bioinformatics, Molecular Modeling Group, Genopode Building, 1015 Lausanne, Switzerland,2 Ludwig Institute for Cancer Research, Ltd., Lausanne, Switzerland,3 Pluridisciplinary Centre for Clinical Oncology (CePO), Lausanne University Hospital (CHUV), Lausanne, Switzerland4
Received 17 July 2009/ Accepted 16 September 2009
Retroelements are important evolutionary forces but can be deleterious if left uncontrolled. Members of the human APOBEC3 family of cytidine deaminases can inhibit a wide range of endogenous, as well as exogenous, retroelements. These enzymes are structurally organized in one or two domains comprising a zinc-coordinating motif. APOBEC3G contains two such domains, only the C terminal of which is endowed with editing activity, while its N-terminal counterpart binds RNA, promotes homo-oligomerization, and is necessary for packaging into human immunodeficiency virus type 1 (HIV-1) virions. Here, we performed a large-scale mutagenesis-based analysis of the APOBEC3G N terminus, testing mutants for (i) inhibition of vif-defective HIV-1 infection and Alu retrotransposition, (ii) RNA binding, and (iii) oligomerization. Furthermore, in the absence of structural information on this domain, we used homology modeling to examine the positions of functionally important residues and of residues found to be under positive selection by phylogenetic analyses of primate APOBEC3G genes. Our results reveal the importance of a predicted RNA binding dimerization interface both for packaging into HIV-1 virions and inhibition of both HIV-1 infection and Alu transposition. We further found that the HIV-1-blocking activity of APOBEC3G N-terminal mutants defective for packaging can be almost entirely rescued if their virion incorporation is forced by fusion with Vpr, indicating that the corresponding region of APOBEC3G plays little role in other aspects of its action against this pathogen. Interestingly, residues forming the APOBEC3G dimer interface are highly conserved, contrasting with the rapid evolution of two neighboring surface-exposed amino acid patches, one targeted by the Vif protein of primate lentiviruses and the other of yet-undefined function.
* Corresponding author. Mailing address: Global Health Institute, School of Life Sciences and Frontiers in Genetics National Center for Competence in Research, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland. Phone: 41 21 693 17 51. Fax: 41 21 693 16 35. E-mail: didier.trono{at}epfl.ch
Published ahead of print on 23 September 2009.
Supplemental material for this article may be found at http://jvi.asm.org/.
Present address: Department of Dermatology and Venereology and Department of Microbiology and Molecular Medicine, Geneva University Hospitals and University of Geneva, Geneva, Switzerland.
Journal of Virology, December 2009, p. 12611-12621, Vol. 83, No. 23
0022-538X/09/$08.00+0 doi:10.1128/JVI.01491-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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