Env genes, short for envelope genes, refer to a specific set of genes found in retroviruses. Retroviruses are a type of RNA virus that can convert their RNA genome into DNA, which they then integrate into the host cell's genome. The env genes primarily encode the structural proteins of the viral envelope, which is the outer layer of the retroviral particle.
The envelope proteins play a crucial role in the viral lifecycle as they are responsible for mediating viral entry and fusion with the host cell membrane. These proteins are typically synthesized as large precursor molecules that undergo various modifications to become functional. The final protein products include surface (SU) and transmembrane (TM) subunits, which are usually non-covalently associated.
The SU domain, derived from the N-terminus of the precursor protein, is responsible for binding to specific host receptors, enabling the virus to recognize and attach to target cells. The TM domain, derived from the C-terminus, facilitates the fusion of the viral and host cell membranes, allowing the viral genome to enter the host cell cytoplasm.
Variations in the env genes of retroviruses contribute to their ability to infect different host species and display tropism for specific cell types within those hosts. Consequently, env gene diversity is a critical factor influencing retroviral host range, pathogenesis, and potential for zoonotic transmission.
Given the importance of env genes in viral entry and infection, they are prime targets for therapeutic interventions, such as antiviral drugs and vaccine development, aimed at blocking or inhibiting viral entry into host cells.
