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Fig 1. Modified from http://www.virology.net/Big_Virology/Special/Nermut/Retro.html

HIV-1 is a retrovirus consisting of two linear genomoic-length, positive-sense RNA strands (Fig 1) and fifteen proteins. Frankel, A.D, Young, J.A.T. Annu. Rev. Biochem. 1998. 67: 1-25.

Fig 2. http://medstat.med.utah.edu/WebPath/TUTORIAL/AIDS/AIDS004.html

The HIV-1 viral genome consists of nine open reading frames (ORFs) (Fig 2). Three ORFs are prototypal of retroviridae: Gag, Pol, Env. Gag and Env encode the structural proteins. Gag (group-specific antigen) encodes the proteins that form the viral capsid: Matrix (MA), Capsid (CA), Nucleocapsid (NU), and p6. Env encodes the envelope surface proteins: Surface or gp120 (SU), Transmembrane or gp41 (TM). Pol encodes the three catalytic enzymes: Reverse Transcriptase (RT), Integrase (IN) , and the Protease (PR). The remaining six ORF encode accessory proteins: Vif, Vpr, Nef, Tat, Rev, and Vpu. Tat is a transcriptional activator. Rev participates in the transport of mRNA to the cytoplasm. Vpu promotes degradation of CD4 which is coexpressed with Env in the newly translated molecules. Nef advances the endocytosis and degradation of surface CD4 prior to viral budding thus enhancing Env incorporation into the virion. The functions of Vif and Vpr are less defined:Vif participates in the production of mature virions and Vpr is thought to be involved in the initial stages of viral infectivity. The synthesis of the gag-pol polyprotein occurs by a ribosomal frameshift that occurs infequently, placing Gag and Pol inthe same ORF. Because a frameshift must occur for the pol gene translation, functional Pol proteins are a minor component in comparison with structural products.