An Overview of the Retrovirus Life Cycle

Adsorption: Virus particles first bind to specific receptors on their target cell, which produces changes in the conformation of the envelope glycoprotein such that fusion of the viral and host membranes may occur. After fusion of the viral and host membranes, the virion core is delivered into the cytoplasm of the infected cell.

Uncoating and Production of a Provirus: Once inside the cytoplasm of the infected cell, the virion is disassembled such that the single-stranded RNA genomes of the retrovirus are released from the capsid. The retrovirus then employs the viral enzyme reverse transcriptase to transcribe its single-stranded RNA into single-stranded DNA, degrade the RNA as the DNA is formed, and also produce a complementary DNA strand in order to ultimately synthesize double-stranded proviral DNA from single-stranded viral RNA. The double-stranded DNA is then transported from the cytoplasm into the nucleus of the infected cell, where it is inserted into the host’s genome by the viral enzyme integrase. Once the double-stranded DNA has been inserted into the host’s genome, the virus is now called a provirus.

Translation: Once viral mRNA is transcribed from the DNA provirus inserted in the host genome, it is transported through the nuclear pore into the cytoplasm where it uses the host cell’s ribosomes to translate its genetic information into protein-form. Translation of viral structural proteins, glycoproteins, enzymes, and regulatory proteins is carried out in ribosomes of the infected host cell, contributing to the assembly and egress of new viral particles.