positive regulation by virus of viral protein levels in host cell

Definition

Target type: biologicalprocess

Any process where the infecting virus increases the levels of viral proteins in a cell. [GOC:ai]

Viral proteins play a crucial role in the replication and propagation of viruses within a host cell. To ensure efficient viral replication, viruses have evolved elaborate mechanisms to regulate the levels of their own proteins. One key strategy employed by many viruses is **positive regulation**, where viral proteins themselves or viral-induced cellular factors stimulate the production of additional viral proteins. This can occur at multiple levels, including transcription, translation, and protein stability.

**Transcriptional Regulation:**

* **Viral Transcription Factors:** Many viruses encode their own transcription factors that bind to specific DNA sequences within the viral genome, promoting the transcription of viral genes. These factors can act as activators, enhancing the recruitment of RNA polymerase and increasing the rate of transcription.
* **Viral Enhancers:** Some viruses utilize enhancer elements within their genomes that interact with host cell transcription factors to stimulate the expression of viral genes. These enhancers can be complex and may involve multiple viral and cellular proteins.

**Translational Regulation:**

* **Internal Ribosome Entry Sites (IRES):** Certain viruses employ IRES elements within their mRNA transcripts. These sequences can recruit ribosomes directly, bypassing the need for a 5' cap structure, allowing for efficient translation even in the absence of host cell cap-dependent translation initiation factors.
* **Viral MicroRNAs:** Some viruses produce microRNAs (miRNAs) that target host cell mRNAs, inhibiting their translation. This can indirectly enhance the translation of viral mRNAs by reducing competition for translational machinery.

**Post-Translational Regulation:**

* **Protein Stability:** Viruses can encode proteins that interact with and stabilize viral proteins, preventing their degradation by cellular proteases. This ensures that the levels of critical viral proteins remain high, facilitating viral replication.
* **Viral Proteases:** Some viruses produce proteases that cleave viral polyproteins, generating functional viral proteins. These proteases can also cleave host cell proteins, disrupting cellular processes and creating an environment conducive to viral replication.

**Host Cell Response:**

* **Viral Mimicry:** Some viruses have evolved to mimic host cell proteins, allowing them to hijack cellular pathways and regulate viral protein production. For example, some viral proteins can bind to and activate host cell signaling pathways, leading to the upregulation of viral gene expression.

**Overall, the positive regulation of viral protein levels by viruses is a complex and multi-faceted process involving a range of mechanisms. By effectively controlling their own protein production, viruses ensure their successful replication and propagation within the host cell.'
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Proteins (1)

Compounds (5)