positive regulation of cap-independent translational initiation

Definition

Target type: biologicalprocess

Any process that activates or increases the frequency, rate or extent of cap-independent translational initiation. [GO_REF:0000058, GOC:bf, GOC:PARL, GOC:TermGenie, PMID:11959995]

Positive regulation of cap-independent translational initiation is a complex process that allows for the translation of messenger RNA (mRNA) molecules that lack the typical 5' cap structure. This is crucial for the expression of specific genes, particularly in response to stress, viral infection, and developmental cues. Here is a detailed description of the biological process:

**1. mRNA Recognition and Binding:**
- Unlike cap-dependent translation, where the initiation complex binds to the 5' cap of mRNA, cap-independent translation relies on alternative initiation mechanisms.
- These mechanisms often involve specific RNA structures or sequences located within the 5' untranslated region (UTR) of the mRNA.
- These structures or sequences can recruit specific initiation factors, such as the internal ribosome entry site (IRES), that mediate ribosome binding and initiation.

**2. IRES-Mediated Initiation:**
- IRES elements are highly structured RNA motifs that can directly recruit ribosomes to the mRNA.
- IRES-dependent translation often involves a distinct set of initiation factors, including eIF4G, eIF4A, and eIF3.
- These factors assemble on the IRES and interact with the small ribosomal subunit (40S) to initiate translation.
- The recruitment of ribosomes to the IRES can occur independently of the 5' cap structure, enabling translation initiation at internal sites.

**3. Other Mechanisms of Cap-Independent Initiation:**
- Besides IRES-mediated initiation, other mechanisms can also contribute to cap-independent translation.
- One such mechanism involves the binding of specific initiation factors to the 5' UTR of the mRNA, bypassing the need for a 5' cap.
- These factors can include eIF4G, eIF4A, and other proteins that interact with the mRNA and promote ribosome recruitment.

**4. Translation Initiation and Elongation:**
- Once the ribosome is bound to the mRNA, the translation initiation process proceeds.
- The small ribosomal subunit scans the mRNA for the start codon (AUG) and the large ribosomal subunit joins to form the complete ribosome.
- Translation elongation then proceeds, with the ribosome moving along the mRNA, decoding codons, and adding amino acids to the growing polypeptide chain.

**5. Regulatory Mechanisms:**
- Positive regulation of cap-independent translational initiation is often influenced by cellular conditions and environmental cues.
- For example, stress, viral infection, or developmental signals can trigger the expression of specific proteins involved in cap-independent translation.
- These proteins can regulate the availability and activity of initiation factors, influence the accessibility of IRES elements, or modulate the translation of specific mRNAs.

**6. Significance of Cap-Independent Translation:**
- Cap-independent translation plays a crucial role in gene expression under diverse conditions.
- It allows for the translation of mRNAs that lack a 5' cap, providing flexibility and adaptability in gene regulation.
- This mechanism is particularly important for stress response, viral infection, and developmental processes, where the translation of specific proteins is essential for survival and adaptation.'
"

Proteins (2)

Compounds (2)