title: Mutation of the highly conserved Ser-40 of the HIV-1 p6 gag protein to Phe causes the formation of a hydrophobic patch, enhances membrane association, and polyubiquitination of Gag.
abstract: The HIV-1 p6 Gag protein contains two late assembly (l-) domains that recruit proteins of the endosomal sorting complex required for transport (ESCRT) pathway to mediate membrane fission between the nascent virion and the cell membrane. It was recently demonstrated that mutation of the highly conserved Ser-40 to Phe (S40F) disturbs CA-SP1 processing, virus morphogenesis, and infectivity. It also causes the formation of filopodia-like structures, while virus release remains unaffected. Here, we show that the mutation S40F, but not the conservative mutation to Asp (S40D) or Asn (S40N), augments membrane association, K48-linked polyubiquitination, entry into the 26S proteasome, and, consequently, enhances MHC-I antigen presentation of Gag derived epitopes. Nuclear magnetic resonance (NMR) structure analyses revealed that the newly introduced Phe-40, together with Tyr-36, causes the formation of a hydrophobic patch at the C-terminal α-helix of p6, providing a molecular rationale for the enhanced membrane association of Gag observed in vitro and in HIV-1 expressing cells. The extended exposure of the S40F mutant to unidentified membrane-resident ubiquitin E3-ligases might trigger the polyubiquitination of Gag. The cumulative data support a previous model of a so far undefined property of p6, which, in addition to MA, acts as membrane targeting domain of Gag.
authors.affiliation: Institute of Virology, Friedrich-Alexander-University, 91054 Erlangen, Germany. Friedrich.Hahn@viro.med.uni-erlangen.de.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Hahn
authors.affiliation: Institute of Virology, Friedrich-Alexander-University, 91054 Erlangen, Germany. Christian.Setz@viro.med.uni-erlangen.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Setz
authors.affiliation: Institute of Virology, Friedrich-Alexander-University, 91054 Erlangen, Germany. Melanie.Friedrich@viro.med.uni-erlangen.de.
authors.forename: Melanie
authors.initials: M
authors.lastname: Friedrich
authors.affiliation: Institute of Virology, Friedrich-Alexander-University, 91054 Erlangen, Germany. Pia.Rauch@viro.med.uni-erlangen.de.
authors.forename: Pia
authors.initials: P
authors.lastname: Rauch
authors.affiliation: Department of Chemistry and Centre for Pharmacy, University of Bergen, N-5007 Bergen, Norway. Sara.Solbak@kj.uib.no.
authors.forename: Sara Marie
authors.initials: SM
authors.lastname: Solbak
authors.affiliation: Department of Chemistry and Centre for Pharmacy, University of Bergen, N-5007 Bergen, Norway. Nils.Froystein@kj.uib.no.
authors.forename: Nils Age
authors.initials: NA
authors.lastname: Frøystein
authors.affiliation: Institute of Biochemistry, Charité Universitätsmedizin-Berlin, 10117 Berlin, Germany. Petra.Henklein@charite.de.
authors.forename: Petra
authors.initials: P
authors.lastname: Henklein
authors.affiliation: Institute of Virology, Friedrich-Alexander-University, 91054 Erlangen, Germany. Joerg.Votteler@biochem.utah.edu.
authors.forename: Jörg
authors.initials: J
authors.lastname: Votteler
authors.affiliation: Department of Chemistry and Centre for Pharmacy, University of Bergen, N-5007 Bergen, Norway. Torgils.Fossen@kj.uib.no.
authors.forename: Torgils
authors.initials: T
authors.lastname: Fossen
authors.affiliation: Institute of Virology, Friedrich-Alexander-University, 91054 Erlangen, Germany. Ulrich.Schubert@viro.med.uni-erlangen.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schubert
mesh_terms: D000595:Amino Acid Sequence; D017951:Antigen Presentation; D002462:Cell Membrane / Q000378:metabolism; D000939:Epitopes; D015658:HIV Infections / Q000821:virology*; D015497:HIV-1 / Q000235:genetics* / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D020125:Mutation, Missense; D010649:Phenylalanine / Q000235:genetics*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D000072417:Protein Domains; D012694:Serine / Q000235:genetics*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics; D054875:Ubiquitination; D014771:Virion; D057074:Virus Release; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D000939:Epitopes; D054301:gag Gene Products, Human Immunodeficiency Virus; C083002:p6 gag protein, Human immunodeficiency virus 1; D012694:Serine; D010649:Phenylalanine; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease