title: Nucleocapsid and matrix protein contributions to selective human immunodeficiency virus type 1 genomic RNA packaging.
abstract: The nucleocapsid protein (NC) of retroviruses plays a major role in genomic RNA packaging, and some evidence has implicated the matrix protein (MA) of certain retroviruses in viral RNA binding. To further investigate the role of NC in the selective recognition of genomic viral RNA and to address the potential contribution of MA in this process, we constructed chimeric and deletion human immunodeficiency virus type 1 (HIV-1) mutants that alter the NC or MA protein. Both HIV and mouse mammary tumor virus (MMTV) NC proteins have two zinc-binding domains and similar basic amino acid compositions but differ substantially in total length, amino acid sequence, and spacing of the zinc-binding motifs. When the entire NC coding sequence of HIV was replaced with the MMTV NC coding sequence, we found that the HIV genome was incorporated into virions at 50% of wild-type levels. Viruses produced from chimeric HIV genomes with complete NC replacements, or with the two NC zinc-binding domains replaced with MMTV sequences, preferentially incorporated HIV genomes when both HIV and MMTV genomes were simultaneously present in the cell. Viruses produced from chimeric MMTV genomes in which the MMTV NC had been replaced with HIV NC preferentially incorporated MMTV genomes when both HIV and MMTV genomes were simultaneously present in the cell. In contrast, viruses produced from chimeric HIV genomes containing the Moloney NC, which contains a single zinc-binding motif, were previously shown to preferentially incorporate Moloney genomic RNA. Taken together, these results indicate that an NC protein with two zinc-binding motifs is required for specific HIV RNA packaging and that the amino acid context of these motifs, while contributing to the process, is less crucial for specificity. The data also suggest that HIV NC may not be the exclusive determinant of RNA selectivity. Analysis of an HIV MA mutant revealed that specific RNA packaging does not require MA protein.
authors.affiliation: Department of Medicine, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Poon
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: A
authors.initials: A
authors.lastname: Aldovini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002213:Capsid / Q000235:genetics / Q000378:metabolism*; D036022:Capsid Proteins; D003001:Cloning, Molecular; D015683:Gene Products, gag / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015488:HIV Antigens / Q000235:genetics / Q000378:metabolism*; D016655:HIV Core Protein p24 / Q000032:analysis; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D019251:Nucleocapsid / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000032:analysis; D012367:RNA, Viral; D014407:Tumor Cells, Cultured; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins; D014771:Virion / Q000378:metabolism / Q000648:ultrastructure; D019065:Virus Assembly; D016335:Zinc Fingers; D054301:gag Gene Products, Human Immunodeficiency Virus
chemical_list: D036022:Capsid Proteins; D015683:Gene Products, gag; D015488:HIV Antigens; D016655:HIV Core Protein p24; C071884:NCP7 protein, Human immunodeficiency virus 1; D011498:Protein Precursors; D012367:RNA, Viral; D014763:Viral Matrix Proteins; D014764:Viral Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus; C054858:p17 protein, Human Immunodeficiency Virus Type 1; C059767:p55 gag precursor protein, Human immunodeficiency virus 1