Fig. 2

Functional sites of HIV-1 Gag p6, process of viral budding, and Vpr multifunction in the newly infected cells. (A) Summary of the primary sequence and important functional sites in HIV-1 Gag p6. Two α -helices, H1 and H2, are represented by the light green bars. The binding domains for tumor susceptibility gene 101 (TSG101), ALG-2 interacting protein X (ALIX) and Vpr visually portrayed in dark blue, red, and purple, respectively. Phosphorylation sites are indicated by orange spheres. The attachment sites for ubiquitin (Ub) are depicted as light green spheres, while the attachments sites for small ubiquitin-like modifier 1 (SUMO-1) are designated by light blue spheres. The grey spheres correspond to the glutamic acids that contribute to viral replication. (B) HIV-1 budding process facilitated by Gag p6 and viral replication promoted by Vpr. The Gag p6 recruits endosomal sorting complex required for transport (ESCRT) to facilitate membrane scission and particle release. In subsequent infections, Vpr performs various functions, including promoting the reverse-transcription process, facilitating the nuclear import of the pre-integration complex, inducing cell cycle arrest and apoptosis, transactivating the HIV-LTR, and counteracting host restriction factors