title: Inhibition of CUL4A Neddylation causes a reversible block to SAMHD1-mediated restriction of HIV-1.
abstract: The deoxynucleoside triphosphohydrolase SAMHD1 restricts retroviral replication in myeloid cells. Human immunodeficiency virus type 2 (HIV-2) and a simian immunodeficiency virus from rhesus macaques (SIVmac) encode Vpx, a virion-packaged accessory protein that counteracts SAMHD1 by inducing its degradation. SAMHD1 is thought to work by depleting the pool of intracellular deoxynucleoside triphosphates but has also been reported to have exonuclease activity that could allow it to degrade the viral genomic RNA or viral reverse-transcribed DNA. To induce the degradation of SAMHD1, Vpx co-opts the cullin4a-based E3 ubiquitin ligase, CRL4. E3 ubiquitin ligases are regulated by the covalent attachment of the ubiquitin-like protein Nedd8 to the cullin subunit. Neddylation can be prevented by MLN4924, a drug that inhibits the nedd8-activating enzyme. We report that MLN4924 inhibits the neddylation of CRL4, blocking Vpx-induced degradation of SAMHD1 and maintaining the restriction. Removal of the drug several hours postinfection released the block. Similarly, Vpx-containing virus-like particles and deoxynucleosides added to the cells more than 24 h postinfection released the SAMHD1-mediated block. Taken together, these findings support deoxynucleoside triphosphate pool depletion as the primary mechanism of SAMHD1 restriction and argue against a nucleolytic mechanism, which would not be reversible.
authors.affiliation: Microbiology Department, New York University School of Medicine, New York, New York, USA.
authors.forename: Henning
authors.initials: H
authors.lastname: Hofmann
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Norton
authors.forename: Megan L
authors.initials: ML
authors.lastname: Schultz
authors.forename: Sylvie B
authors.initials: SB
authors.lastname: Polsky
authors.forename: Nicole
authors.initials: N
authors.lastname: Sunseri
authors.forename: Nathaniel R
authors.initials: NR
authors.lastname: Landau
mesh_terms: D002460:Cell Line; D044842:Cullin Proteins / Q000276:immunology / Q000378:metabolism*; D003517:Cyclopentanes / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D015497:HIV-1 / Q000276:immunology* / Q000502:physiology; D006801:Humans; D020559:Monomeric GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D000075687:NEDD8 Protein; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011743:Pyrimidines / Q000378:metabolism; D000076106:SAM Domain and HD Domain-Containing Protein 1; D014452:Ubiquitins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014779:Virus Replication
chemical_list: C114234:CUL4A protein, human; D044842:Cullin Proteins; D003517:Cyclopentanes; D004791:Enzyme Inhibitors; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D011743:Pyrimidines; D014452:Ubiquitins; D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; D020559:Monomeric GTP-Binding Proteins; C539933:pevonedistat