| Structural highlights
Function
POT1_SCHPO Single-stranded telomeric DNA-binding protein that is required to protect the 3'-end telomeric overhang. It binds the consensus sequence 5'-GGTTAC-3'. Regulates telomerase and telomere length.[1] [2] [3] ABC3G_HUMAN DNA deaminase (cytidine deaminase) that mediates a form of innate resistance to retroviral infections (at least to HIV-1 infection) by triggering G-to-A hypermutation in the newly synthesized viral DNA. The replacements C-to-U in the minus strand DNA of HIV-1 during reverse transcription, leads to G-to-A transitions in the plus strand. The inhibition of viral replication is either due to the degradation of the minus strand before its integration or to the lethality of the hypermutations. Modification of both DNA strands is not excluded. This antiviral activity is neutralized by the virion infectivity factor (VIF), that prevents the incorporation of APOBEC3G into progeny HIV-1 virions by both inhibiting its translation and/or by inducing its ubiquitination and subsequent degradation by the 26S proteasome. May also prevent the transposition of a subset of retroelements. Binds a variety of RNAs, but does not display detectable APOB, NF1 and NAT1 mRNA editing.[4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]
Publication Abstract from PubMed
Human apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3 (A3) proteins are a family of cytidine deaminases that catalyze the conversion of deoxycytidine (dC) to deoxyuridine (dU) in single-stranded DNA (ssDNA). A3 proteins act in the innate immune response to viral infection by mutating the viral ssDNA. One of the most well-studied human A3 family members is A3G, which is a potent inhibitor of HIV-1. Each A3 protein prefers a specific substrate sequence for catalysis-for example, A3G deaminates the third dC in the CCCA sequence motif. However, the interaction between A3G and ssDNA is difficult to characterize due to poor solution behavior of the full-length protein and loss of DNA affinity of the truncated protein. Here, we present a novel DNA-anchoring fusion strategy using the protection of telomeres protein 1 (Pot1) which has nanomolar affinity for ssDNA, with which we captured an A3G-ssDNA interaction. We crystallized a non-preferred adenine in the -1 nucleotide-binding pocket of A3G. The structure reveals a unique conformation of the catalytic site loops that sheds light onto how the enzyme scans substrate in the -1 pocket. Furthermore, our biochemistry and virology studies provide evidence that the nucleotide-binding pockets on A3G influence each other in selecting the preferred DNA substrate. Together, the results provide insights into the mechanism by which A3G selects and deaminates its preferred substrates and help define how A3 proteins are tailored to recognize specific DNA sequences. This knowledge contributes to a better understanding of the mechanism of DNA substrate selection by A3G, as well as A3G antiviral activity against HIV-1.
Insights into DNA substrate selection by APOBEC3G from structural, biochemical, and functional studies.,Ziegler SJ, Liu C, Landau M, Buzovetsky O, Desimmie BA, Zhao Q, Sasaki T, Burdick RC, Pathak VK, Anderson KS, Xiong Y PLoS One. 2018 Mar 29;13(3):e0195048. doi: 10.1371/journal.pone.0195048., eCollection 2018. PMID:29596531[16]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Baumann P, Cech TR. Pot1, the putative telomere end-binding protein in fission yeast and humans. Science. 2001 May 11;292(5519):1171-5. PMID:11349150 doi:http://dx.doi.org/10.1126/science.1060036
- ↑ Lei M, Baumann P, Cech TR. Cooperative binding of single-stranded telomeric DNA by the Pot1 protein of Schizosaccharomyces pombe. Biochemistry. 2002 Dec 10;41(49):14560-8. PMID:12463756
- ↑ Miyoshi T, Kanoh J, Saito M, Ishikawa F. Fission yeast Pot1-Tpp1 protects telomeres and regulates telomere length. Science. 2008 Jun 6;320(5881):1341-4. doi: 10.1126/science.1154819. PMID:18535244 doi:http://dx.doi.org/10.1126/science.1154819
- ↑ Kao S, Khan MA, Miyagi E, Plishka R, Buckler-White A, Strebel K. The human immunodeficiency virus type 1 Vif protein reduces intracellular expression and inhibits packaging of APOBEC3G (CEM15), a cellular inhibitor of virus infectivity. J Virol. 2003 Nov;77(21):11398-407. PMID:14557625
- ↑ Sheehy AM, Gaddis NC, Choi JD, Malim MH. Isolation of a human gene that inhibits HIV-1 infection and is suppressed by the viral Vif protein. Nature. 2002 Aug 8;418(6898):646-50. Epub 2002 Jul 14. PMID:12167863 doi:10.1038/nature00939
- ↑ Mangeat B, Turelli P, Caron G, Friedli M, Perrin L, Trono D. Broad antiretroviral defence by human APOBEC3G through lethal editing of nascent reverse transcripts. Nature. 2003 Jul 3;424(6944):99-103. Epub 2003 May 28. PMID:12808466 doi:10.1038/nature01709
- ↑ Harris RS, Bishop KN, Sheehy AM, Craig HM, Petersen-Mahrt SK, Watt IN, Neuberger MS, Malim MH. DNA deamination mediates innate immunity to retroviral infection. Cell. 2003 Jun 13;113(6):803-9. PMID:12809610
- ↑ Zhang H, Yang B, Pomerantz RJ, Zhang C, Arunachalam SC, Gao L. The cytidine deaminase CEM15 induces hypermutation in newly synthesized HIV-1 DNA. Nature. 2003 Jul 3;424(6944):94-8. Epub 2003 May 28. PMID:12808465 doi:10.1038/nature01707
- ↑ Mariani R, Chen D, Schrofelbauer B, Navarro F, Konig R, Bollman B, Munk C, Nymark-McMahon H, Landau NR. Species-specific exclusion of APOBEC3G from HIV-1 virions by Vif. Cell. 2003 Jul 11;114(1):21-31. PMID:12859895
- ↑ Shindo K, Takaori-Kondo A, Kobayashi M, Abudu A, Fukunaga K, Uchiyama T. The enzymatic activity of CEM15/Apobec-3G is essential for the regulation of the infectivity of HIV-1 virion but not a sole determinant of its antiviral activity. J Biol Chem. 2003 Nov 7;278(45):44412-6. Epub 2003 Sep 11. PMID:12970355 doi:http://dx.doi.org/10.1074/jbc.C300376200
- ↑ Sheehy AM, Gaddis NC, Malim MH. The antiretroviral enzyme APOBEC3G is degraded by the proteasome in response to HIV-1 Vif. Nat Med. 2003 Nov;9(11):1404-7. Epub 2003 Oct 5. PMID:14528300 doi:10.1038/nm945
- ↑ Turelli P, Mangeat B, Jost S, Vianin S, Trono D. Inhibition of hepatitis B virus replication by APOBEC3G. Science. 2004 Mar 19;303(5665):1829. PMID:15031497 doi:10.1126/science.1092066
- ↑ Chen H, Lilley CE, Yu Q, Lee DV, Chou J, Narvaiza I, Landau NR, Weitzman MD. APOBEC3A is a potent inhibitor of adeno-associated virus and retrotransposons. Curr Biol. 2006 Mar 7;16(5):480-5. PMID:16527742 doi:10.1016/j.cub.2006.01.031
- ↑ Bulliard Y, Narvaiza I, Bertero A, Peddi S, Rohrig UF, Ortiz M, Zoete V, Castro-Diaz N, Turelli P, Telenti A, Michielin O, Weitzman MD, Trono D. Structure-function analyses point to a polynucleotide-accommodating groove essential for APOBEC3A restriction activities. J Virol. 2011 Feb;85(4):1765-76. doi: 10.1128/JVI.01651-10. Epub 2010 Dec 1. PMID:21123384 doi:10.1128/JVI.01651-10
- ↑ Chen KM, Harjes E, Gross PJ, Fahmy A, Lu Y, Shindo K, Harris RS, Matsuo H. Structure of the DNA deaminase domain of the HIV-1 restriction factor APOBEC3G. Nature. 2008 Mar 6;452(7183):116-9. Epub 2008 Feb 20. PMID:18288108 doi:10.1038/nature06638
- ↑ Ziegler SJ, Liu C, Landau M, Buzovetsky O, Desimmie BA, Zhao Q, Sasaki T, Burdick RC, Pathak VK, Anderson KS, Xiong Y. Insights into DNA substrate selection by APOBEC3G from structural, biochemical, and functional studies. PLoS One. 2018 Mar 29;13(3):e0195048. doi: 10.1371/journal.pone.0195048., eCollection 2018. PMID:29596531 doi:http://dx.doi.org/10.1371/journal.pone.0195048
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