Alteration of the Proline at Position 7 of the HIV-1 Spacer Peptide p1 Suppresses Viral Infectivity in a Strain Dependent Manner

Abstract

The HIV-1 spacer peptide p1 is located in the C-terminus of the Gag polyprotein and separates the nucleocapsid (NC) and p6(Gag). Research centered on p1 has been limited and as yet no function has been ascribed to this spacer peptide. We have previously found that the conserved p1 proline residues (position 7 and 13) are critical for replication in the HIV-1 strain HXB2-BH10. In this study we have focused on the proline rich p1-p6(Gag) C-terminus of HIV-1. We individually examined the role of p1 proline's in multiple strains of HIV-1 and investigated the role of three proline residues in p6(Gag) (P24, P25 and P30). Assessment of the HXB2-BH10 based mutants revealed that Gag-Pol incorporation relative to Gag decreased in the p1 mutant virions, with the double proline mutant the most impaired. Mutating both p1 proline residues was found to abolish infectivity in multiple strains of HIV-1. Independent mutation of the p1 proline at position 7 resulted in a strain-dependent suppression of viral infectivity. This defect correlates with the presence of a tyrosine residue at position 9 of p1 and occurs in the early phase of the HIV-1 replication cycle. The p1 proline residues were found to be functionally distinct from P24, P25 and P30 in p6(Gag). This work affords novel insights into our understanding of the role of p1 in HIV-1 replication.

Multiple T-cell epitopes overlap positively-selected residues in the p1 spacer protein of HIV-1 gag

“…1b) [2,7]. Mutations in this region, particularly the proline residues at positions 7 and 13, negatively affect protein processing, RNA dimer stability and abolish viral infectivity in multiple strains of HIV-1 [7].…”

“…1b) [2,7]. Mutations in this region, particularly the proline residues at positions 7 and 13, negatively affect protein processing, RNA dimer stability and abolish viral infectivity in multiple strains of HIV-1 [7]. Although the role of p1 in viral replication is not well understood, it has been suggested that mutations in p1 impact nucleocapsid function, which is important in the early stages of reverse transcription and integration [7].…”

Incoming HIV virion-derived Gag Spacer Peptide 2 (p1) is a target of effective CD8+ T cell antiviral responses

“…Additionally, it is present in both gag and pol open reading frames. Mutations (e.g., P at position 7) can affect processing, RNA dimer stability, and infectivity (Hill et al, 2007). Mutations in Gag SP2 may affect nucleocapsid function, particularly in early stages of reverse transcription and integration, yet SP2 appears to play a minor role in viral infectivity (de Marco et al, 2012).…”

How HIV-1 Gag Manipulates Its Host Cell Proteins: A Focus on Interactors of the Nucleocapsid Domain

“…Mutagenesis studies suggest a possible implication of its proline residues in the processing of Gag polyprotein, the control of gRNA dimer stability and the packaging of Gag-Pol into nascent virions. These mutations also abolish the infectivity of multiple HIV-1 strains in peripheral blood monolayer cells [213]. While the proper processing between NC and p6 appears crucial for viral infectivity and maturation, the SP2 itself seems dispensable, and its deletion has only minor effect on the viral infectivity [214].…”