The two zinc fingers in the human immunodeficiency virus type 1 nucleocapsid protein are not functionally equivalent.
The highly conserved zinc fingers in retroviral nucleocapsid (NC) proteins have the general structure Cys-(X)2-Cys-(X)4-His-(X)4-Cys. Human immunodeficiency virus type 1 (HIV-1) contains two Zn2+ fingers, and mutants were constructed in which the native sequence of each Zn2+ finger was maintained but their positions in the NC protein were changed. Mutants had either two first-finger sequences (pNC1/1), two second-finger sequences (pNC2/2), or reversed first- and second-finger sequences (pNC2/1). Cells transfected with mutant or wild-type clones produced similar levels of Tat, Gag, Pol, and Env proteins, formed syncytia, and shed viruslike particles that were indistinguishable by electron microscopy. However, the pNC2/1 and pNC2/2 mutants were inefficient in packaging genomic RNA (less than 15% of wild-type levels), whereas the pNC1/1 mutant packaged approximately 70% of wild-type levels of RNA. No infectious virus could be detected with either the pNC2/1 or pNC2/2 mutants, whereas the pNC1/1 mutant appeared to sustain a low level of replication and reverted to a competent wild-type-like viral species after a 2- to 4-week lag period. The data strongly suggest that the two Zn2+ fingers of HIV-1 are not functionally equivalent and that the first Zn2+ finger in the Gag precursor plays a more prominent role in RNA selection and packaging. The data also indicate that both Zn2+ fingers in the mature NC protein play as yet unknown roles in viral assembly or the early stages of the viral infection process.
AIDS Vaccine Development Program, Program Resources Inc., DynCorp, Frederick, Maryland.
R J
RJ
Gorelick
D J
DJ
Chabot
A
A
Rein
L E
LE
Henderson
L O
LO
Arthur
D000595:Amino Acid Sequence; D001483:Base Sequence; D036022:Capsid Proteins; D015683:Gene Products, gag / Q000737:chemistry*; D015497:HIV-1 / Q000737:chemistry* / Q000254:growth & development; D006367:HeLa Cells; D006801:Humans; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D012367:RNA, Viral / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry; D013329:Structure-Activity Relationship; D014162:Transfection; D014764:Viral Proteins; D014779:Virus Replication; D016335:Zinc Fingers; D054301:gag Gene Products, Human Immunodeficiency Virus
D036022:Capsid Proteins; D015683:Gene Products, gag; C071884:NCP7 protein, Human immunodeficiency virus 1; D009838:Oligodeoxyribonucleotides; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D014764:Viral Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus