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. 2022 Jul 8;23(14):7569. doi: 10.3390/ijms23147569

Table 1.

Summary of known functional roles employed by the HIV-1 Gag domains in viral replication and infectivity.

Gag Domain Summarized Functional Roles
Matrix;
p17
  • Facilitates targeting of Gag–Pol and Gag to the plasma membrane

  • Incorporation of Env into virions

  • Associated with reverse transcription and the pre-integration complex during early stages of replication

  • Binds tRNA (transfer RNA), rRNA (ribosomal RNA) and heterologous DNA

  • Acts as a viral cytokine to promote a favourable network of virus- and host-derived stimulatory factors for optimal infection and replication

Capsid;
p24
  • Houses viral RNA and core-associated proteins

  • Interaction with several cellular host factors and/or metabolites including cyclophilin A and inositol hexaphosphate (IP6)

  • Interacts with cellular nucleoporins to allow import of the PIC

  • The precursor PR55 Gag capsid domain and the mature p24 capsid display several functional roles in the viral replication cycle, including assembly, reverse transcription, integration and infectivity

Nucleocapsid;
p7
  • Packages viral RNA into rapidly assembling, immature viral particles

  • Ability to renature nucleic acids

  • Stimulates tRNALys binding to the primer binding site, initiates reverse transcription from the bound tRNALys and partakes in strand transfer

  • Possesses nucleic binding and chaperone activity in the conversion of gRNA (genomic RNA) to viral dsDNA (double-stranded DNA)

p6
  • Flexible docking site for cellular host factors, specifically ALIX and TSG101

  • Contributes to RNA binding specificity of gRNA of Gag PR55

  • Incorporation of viral accessory protein, Vpr

  • Primary phosphoprotein

  • Substrate for virus-associated kinases such as Erk-2 and Elk tyrosine kinases

  • Contributes to RNA binding specificity of PR55 Gag

SP1
  • May have active roles in viral assembly and possibly infectivity

  • Associated with Gag–Gag interactions in budding of immature virus particles

SP2
  • Plays a role in the incorporation of Pol and Gag in the immature virus particles

  • Effect on the stability of nucleocapsid-RNA (NC–RNA) complexes and thus viral infectivity

  • May have an effect on proviral integration when present as the p9 NC|SP2 peptide