title: 4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) inhibits HIV-1 reverse transcriptase with multiple mechanisms.
abstract: 4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) is a nucleoside analog that, unlike approved anti-human immunodeficiency virus type 1 (HIV-1) nucleoside reverse transcriptase inhibitors, has a 3'-OH and exhibits remarkable potency against wild-type and drug-resistant HIVs. EFdA triphosphate (EFdA-TP) is unique among nucleoside reverse transcriptase inhibitors because it inhibits HIV-1 reverse transcriptase (RT) with multiple mechanisms. (a) EFdA-TP can block RT as a translocation-defective RT inhibitor that dramatically slows DNA synthesis, acting as a de facto immediate chain terminator. Although non-translocated EFdA-MP-terminated primers can be unblocked, they can be efficiently converted back to the EFdA-MP-terminated form. (b) EFdA-TP can function as a delayed chain terminator, allowing incorporation of an additional dNTP before blocking DNA synthesis. In such cases, EFdA-MP-terminated primers are protected from excision. (c) EFdA-MP can be efficiently misincorporated by RT, leading to mismatched primers that are extremely hard to extend and are also protected from excision. The context of template sequence defines the relative contribution of each mechanism and affects the affinity of EFdA-MP for potential incorporation sites, explaining in part the lack of antagonism between EFdA and tenofovir. Changes in the type of nucleotide before EFdA-MP incorporation can alter its mechanism of inhibition from delayed chain terminator to immediate chain terminator. The versatility of EFdA in inhibiting HIV replication by multiple mechanisms may explain why resistance to EFdA is more difficult to emerge.
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Eleftherios
authors: E
authors: Michailidis
authors: From the Christopher Bond Life Sciences Center and Departments of Veterinary Pathobiology and.
authors: Andrew D
authors: AD
authors: Huber
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Emily M
authors: EM
authors: Ryan
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Yee T
authors: YT
authors: Ong
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Maxwell D
authors: MD
authors: Leslie
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Kayla B
authors: KB
authors: Matzek
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Kamalendra
authors: K
authors: Singh
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Bruno
authors: B
authors: Marchand
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Ariel N
authors: AN
authors: Hagedorn
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211.
authors: Karen A
authors: KA
authors: Kirby
authors: Magee-Womens Research Institute and Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.
authors: Lisa C
authors: LC
authors: Rohan
authors: Division of Emerging Infectious Diseases, Tohoku University, Sendai 980-8575, Japan.
authors: Eiichi N
authors: EN
authors: Kodama
authors: Department of Internal Medicine, Kumamoto University, Kumamoto 860-8556, Japan, Experimental Retrovirology Section, HIV/AIDS Malignancy Branch, National Institutes of Health, Bethesda, Maryland 20892, and.
authors: Hiroaki
authors: H
authors: Mitsuya
authors: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15219.
authors: Michael A
authors: MA
authors: Parniak
authors: From the Christopher Bond Life Sciences Center and Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65211, Biochemistry, University of Missouri, Columbia, Missouri 65211, sarafianoss@missouri.edu.
authors: Stefan G
authors: SG
authors: Sarafianos
mesh_terms: D001483:Base Sequence; D020134:Catalytic Domain; D002460:Cell Line; D017931:DNA Primers; D003839:Deoxyadenosines / Q000494:pharmacology*; D054303:HIV Reverse Transcriptase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007700:Kinetics; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*; D020349:Surface Plasmon Resonance
chemical_list: D017931:DNA Primers; D003839:Deoxyadenosines; D018894:Reverse Transcriptase Inhibitors; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase; C558823:islatravir
keywords: AIDS; Antivirals; EFdA; Enzyme Inhibitor; Human Immunodeficiency Virus (HIV); NRTIs; Nucleoside/Nucleotide Analogue; Reverse Transcriptase; Reverse Transcription