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#initiation factors

2 public questions tagged with this topic.

Translation in Prokaryotes and Eukaryotes

Circularization of mRNA in eukaryotes is mediated by

High efficiency eukaryotic translation involves circularization of mRNA into a closed-loop topology that enhances recycling and stability. eIF4G acts as a large scaffold that simultaneously binds eIF4E attached to the 5' cap via its N-terminal domain and poly(A)-binding protein PABP bound to the 3' poly(A) tail via its C-terminal domain. The eIF4E-eIF4G-PABP interaction brings ends together, enhancing 40S subunit recycling from termination to initiation, stabilizing mRNA against deadenylation-mediated decay, and increasing affinity of eIF4F for cap. eIF2 delivers initiator tRNA and eEF2 contro

Ref: Alberts Fig 6-71 Closed-loop model; NCBI Review - eIF4G-PABP bridge circularizes mRNA to promote translation

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Translation in Prokaryotes and Eukaryotes

IRES allows translation in absence of

IRES elements circumvent the requirement for the 7-methylguanosine cap and the eIF4E component of eIF4F complex. Instead of 5' end scanning, the IRES tertiary fold creates a landing pad mimicking initiator tRNA or eIF4G binding surfaces, allowing direct 40S and eIF3 recruitment near the initiation codon without scanning from the terminus. This independence permits protein synthesis when viral proteases cleave eIF4G or when cellular stress depletes cap-binding capacity. Poly(A) tail, functional ribosomes, initiator tRNA, and elongation factors remain essential for translation, yet the cap struc

Ref: NCBI Bookshelf PMCID PMC478336; Lodish Molecular Cell Biology 8th Ed, Figure 4-27 - IRES facilitates cap-independent ribosome recruitment

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