Eukaryotic Initiation Factor - EIF4 (eIF4F)

EIF4 (eIF4F)

The eIF4 initiation factors include eIF4A, eIF4B, eIF4E, and eIF4G. eIF4F is often used to refer to the complex of eIF4A, eIF4E, and eIF4G.

eIF4G is a scaffolding protein that interacts with eIF3 (see below), as well as the other members of the eIF4F complex. eIF4E recognizes and binds to the 5' cap structure of mRNA, while eIF4G binds to Poly(A)-binding protein, which binds the poly(A) tail, circularizing and activating the bound mRNA.

eIF4A – a DEAD box RNA helicase – is important for resolving mRNA secondary structures. eIF4B contains two RNA-binding domains – one non-specifically interacts with mRNA, whereas the second specifically binds the 18S portion of the small ribosomal subunit. It acts as an anchor, as well as a critical co-factor for eIF4A. It is a substrate of S6K, and, when phosphorylated, it promotes the formation of the pre-initiation complex. In vertebrates, eIF4H is an additional initiation factor with similar function to eIF4B.