Infected cells can survive while viruses are being replicated and released.

Release- New viruses formed come out of the host’s cell and it can infect other cells of the host.

Assembly- The new viral components formed are assembled near the cell surface and form new viruses.

env gene is translated into envelope protein.

pol gene is transcribed into reverse transcriptase.

gag gene is translated into capsid protein.

The host’s ribosome translates the viral gene into protein, translation takes place in the cytosol of the host’s cell. Packaging signal sequence of “P” in the viral genome allows incorporation of the newly synthesized RNA into the new virus. Each end of the viral genome has a repeated sequence of “R” that enhances the integration and the host's cells transcribe at a faster rate.

Replication- The virus uses the host's machinery to transcribe and translate viral genes and produce new viral components.

Genome Integration- Inside the nucleus, a special viral enzyme integrates the viral DNA with the host’s cell DNA.

Viral DNA is incorporated into the host's genome.

Reverse Transcription- Viral RNA turns into the DNA to become compatible with the host's cell genome.

Invasion- The envelope around the virus merges with the membrane of the host's cell and the viral RNA moves into the cell.

Binding- The virus attaches to the surface of the host’s cell.

It is the env proteins that make the retrovirus infectious.įollowing steps are involved in the life cycle of the retrovirus.

Env proteins- It plays the role in the entrance of virion into the host's cell.

Pol proteins- It functions for the synthesis of viral DNA and integration into host cell DNA after infection.

It is responsible for proteolytic cleavages during virion maturation to form mature gag and pol protein. Protease- Its appearance is different in different viruses.Group-specific antigen (gag) proteins- It is the major component of viral capsid and possesses matrix (MA) and nucleocapsid (NC) as the two nucleic acid binding domains.Proteins- It consists of four kinds of proteins, gag proteins, pol proteins, protease, and env proteins.The internal regions encode virion proteins for gene expression. At the terminal, it has non-coding regions which help in replication. RNA- It consists of a dimer RNA which has a 5’ cap at and a 3’ poly-A tail.

It enables retrovirus to directly enter the cell by fusing with their membrane.It permits the entry and exit of retrovirus through the host’s cell via endothermal membrane trafficking.The lipid bilayer provides protection to the retrovirus from the extracellular environment.It is responsible for the following three functions. Envelop- It is composed of lipids as well as glycoproteins encoded by env genes.

Retrovirus