The Structural Basis of APOBEC Functions The APOBEC (Apolioprotein B mRNA-editing Enzyme Catalytic polypeptide) family of cytidine deaminases is a family of enzymes that deaminate cytidine residues of DNA/RNA. APOBEC proteins possess significant cellular functions and anti-viral activity, which partially accounts for the intense attention to this the field of research in recent years. APOBEC proteins are found only in vertebrates and APOBEC3 (Apo3) proteins are found only in primates. By binding and deaminating DNA/RNA, APOBEC enzymes achieve remarkably diverse cellular functions. For example, APOBEC1 (Apo1) edits the mRNA of a protein involved in lipid metabolism;AID plays a key role in somatic hypermutation for antibody maturation;APOBEC2 (Apo2) may play a regulatory role for heart muscle development;and Apo3 proteins, especially Apo3G, can restrict important viral pathogens, including Human Immunodeficiency Virus (HIV) and Hepatitis B Virus (HBV), and retro-element mobility. As a result, a novel approach to HIV therapy focuses on utilizing the potent anti-viral activity of Apo3G and Apo3F. Our long-term goals are to understand the structural/functional relationship for APOBEC cellular function and their anti-viral activity.
Our specific aims are to extend our prior success in the structural characterization of APOBEC proteins to the studies of the structural basis of APOBEC's functional mechanisms, including their antiviral activity, with particular focuses on Apo3G and Apo3F. The research will provide valuable information for understanding the molecular details of the APOBEC enzyme family and for the potential drug development to provide therapy for HIV, immune diseases and other diseases related to APOBEC function or malfunction.

Public Health Relevance

Understanding The Structural Basis of APOBEC Functions The Apolioprotein B mRNA-editing enzyme catalytic polypeptide (APOBEC) family of cytidine deaminases are found exclusively in verterbrates. APOBEC nucleic acid deaminases modify genes by deaminating cytosines in mRNA coding sequences and in ssDNA. Their critical biological roles include lipid metabolism, humoral immune response, and potential regulations of developmental process of certain human organs and reproductive system. Additionally, these enzymes can inhibit the replication of retroviruses, such as the human immunodeficiency virus (HIV) and hepatitis B virus (HBV), and retrotransposons. The important beneficial mutational ability of APOBEC proteins can become detrimental to the stability of genome if their activity is not tightly regulated. The understanding of the structural basis of the molecular mechanisms of APOBEC function, which is still poorly understood, bears scientific significance and direct health relevance. We propose to study the structure/function of this important APOBEC deaminase family, with focuses on APOBEC3G and 3F (Apo3G and 3F) proteins and their interactions with cellular and viral ligands, using mainly structural biology, assisted by biophysics, molecular biology, and functional biochemistry.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
AIDS Molecular and Cellular Biology Study Section (AMCB)
Program Officer
Sakalian, Michael
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Southern California
Schools of Arts and Sciences
Los Angeles
United States
Zip Code
Fang, Yao; Xiao, Xiao; Li, Shu-Xing et al. (2018) Molecular Interactions of a DNA Modifying Enzyme APOBEC3F Catalytic Domain with a Single-Stranded DNA. J Mol Biol 430:87-101
Ito, Fumiaki; Yang, Hanjing; Xiao, Xiao et al. (2018) Understanding the Structure, Multimerization, Subcellular Localization and mC Selectivity of a Genomic Mutator and Anti-HIV Factor APOBEC3H. Sci Rep 8:3763
Xiao, Xiao; Yang, Hanjing; Arutiunian, Vagan et al. (2017) Structural determinants of APOBEC3B non-catalytic domain for molecular assembly and catalytic regulation. Nucleic Acids Res 45:7540
Xiao, Xiao; Yang, Hanjing; Arutiunian, Vagan et al. (2017) Structural determinants of APOBEC3B non-catalytic domain for molecular assembly and catalytic regulation. Nucleic Acids Res 45:7494-7506
Ito, Fumiaki; Fu, Yang; Kao, Shen-Chi A et al. (2017) Family-Wide Comparative Analysis of Cytidine and Methylcytidine Deamination by Eleven Human APOBEC Proteins. J Mol Biol 429:1787-1799
Xiao, Xiao; Li, Shu-Xing; Yang, Hanjing et al. (2016) Crystal structures of APOBEC3G N-domain alone and its complex with DNA. Nat Commun 7:12193
Chen, Qihan; Xiao, Xiao; Wolfe, Aaron et al. (2016) The in vitro Biochemical Characterization of an HIV-1 Restriction Factor APOBEC3F: Importance of Loop 7 on Both CD1 and CD2 for DNA Binding and Deamination. J Mol Biol 428:2661-70
Gu, Jiang; Chen, Qihan; Xiao, Xiao et al. (2016) Biochemical Characterization of APOBEC3H Variants: Implications for Their HIV-1 Restriction Activity and mC Modification. J Mol Biol 428:4626-4638
Fu, Yang; Ito, Fumiaki; Zhang, Gewen et al. (2015) DNA cytosine and methylcytosine deamination by APOBEC3B: enhancing methylcytosine deamination by engineering APOBEC3B. Biochem J 471:25-35
Wang, Wenbo; Zirkle, Brett; Nie, Jianhui et al. (2015) N463 Glycosylation Site on V5 Loop of a Mutant gp120 Regulates the Sensitivity of HIV-1 to Neutralizing Monoclonal Antibodies VRC01/03. J Acquir Immune Defic Syndr 69:270-7

Showing the most recent 10 out of 16 publications