Specific binding of HIV-1 nucleocapsid protein to PSI RNA in vitro requires N-terminal zinc finger and flanking basic amino acid residues

EMBO J. 1994 Apr 1;13(7):1525-33.


The nucleocapsid (NC) protein of human immunodeficiency virus HIV-1 (NCp7) is responsible for packaging the viral RNA by recognizing a packaging site (PSI) on the viral RNA genome. NCp7 is a molecule of 55 amino acids containing two zinc fingers, with only the first one being highly conserved among retroviruses. The first zinc finger is flanked by two basic amino acid clusters. Here we demonstrate that chemically synthesized NCp7 specifically binds to viral RNA containing the PSI using competitive filter binding assays. Deletion of the PSI from the RNA abrogates this effect. The 35 N-terminal amino acids of NCp7, comprising the first zinc finger, are sufficient for specific RNA binding. Chemically synthesized mutants of the first zinc finger demonstrate that the amino acid residues C-C-C/H-C/H are required for specific RNA binding and zinc coordination. Amino acid residues F16 and T24, but not K20, E21 and G22, located within this zinc finger, are essential for specific RNA binding as well. The second zinc finger cannot replace the first one. Furthermore, mutations in the basic amino acid residues flanking the first zinc finger demonstrate that R3, 7, 10, 29 and 32 but not K11, 14, 33 and 34 are also essential for specific binding. Specific binding to viral RNA is also observed with recombinant NCp15 and Pr55Gag. The results demonstrate for the first time specific interaction of a retroviral NC protein with its PSI RNA in vitro.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Capsid / genetics
  • Capsid / metabolism*
  • Capsid Proteins*
  • DNA Mutational Analysis
  • Gene Products, gag / genetics
  • Gene Products, gag / metabolism*
  • HIV-1 / metabolism*
  • Molecular Sequence Data
  • Nucleocapsid Proteins*
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / genetics
  • Protein Binding
  • Protein Precursors / genetics
  • Protein Precursors / metabolism
  • RNA, Viral / metabolism*
  • Recombinant Proteins / metabolism
  • Viral Proteins*
  • Zinc Fingers*
  • gag Gene Products, Human Immunodeficiency Virus


  • Capsid Proteins
  • Gene Products, gag
  • NCP7 protein, Human immunodeficiency virus 1
  • Nucleocapsid Proteins
  • Peptide Fragments
  • Protein Precursors
  • RNA, Viral
  • Recombinant Proteins
  • Viral Proteins
  • gag Gene Products, Human Immunodeficiency Virus
  • p15 gag protein, Human immunodeficiency virus 1
  • p55 gag precursor protein, Human immunodeficiency virus 1