1. Hijacking Cellular Machinery:
* Transcription and Translation: Viruses inject their genetic material (DNA or RNA) into the host cell. This genetic material then commandeers the host cell's machinery for transcription (copying DNA into RNA) and translation (using RNA to create viral proteins). The host cell essentially becomes a viral protein factory.
* Replication: Viruses rely on the host cell's enzymes and resources to replicate their own genetic material. They may even integrate their DNA into the host genome, ensuring continued replication.
2. Altering Cellular Processes:
* Metabolic pathways: Viruses can alter host cell metabolism to favor their own replication. For instance, they may redirect the production of amino acids or nucleotides to prioritize viral protein synthesis.
* Cell cycle regulation: Some viruses can manipulate the host cell's cell cycle, forcing it to continuously divide, providing more resources for viral replication.
* Immune response suppression: Many viruses have evolved mechanisms to evade the host's immune system. They can suppress immune signaling pathways or even directly target immune cells.
3. Viral Proteins with Specific Functions:
* Viral proteins can directly interact with host cell proteins to alter their activity or localization.
* They can act as enzymes involved in replication, transcription, and other viral processes.
* They can interfere with host cell signaling pathways, disrupting normal cellular functions.
Examples:
* HIV: This virus integrates its DNA into the host cell's genome, leading to persistent infection.
* Influenza virus: It uses host cell enzymes to replicate and release new viral particles.
* Herpes virus: It can remain dormant in the host cell, reactivating when triggered, causing recurrent infections.
In conclusion: Viral genes are highly efficient at manipulating host cell functions for their own propagation. This ability to redirect host cell activity is the core strategy of viral survival and infection.
