What is the importance of eIF4E factor?
eIF4E is a eukaryotic translation initiation factor involved in directing ribosomes to the cap structure of mRNAs. It is a 24-kD polypeptide that exists as both a free form and as part of the eIF4F pre-initiation complex. Almost all cellular mRNA require eIF4E in order to be translated into protein.
What is the role of the enzyme eIF4E?
eIF4E is the cap-binding protein which, in synergy with proteins such as the helicase eIF4A and the scaffolding protein eIF4G, binds to mRNA, allowing the recruitment of ribosomes and translation initiation.
Which eukaryotic initiation factor binds the cap?
factor 4E
The cap binding protein, eukaryotic initiation factor 4E (eIF-4E), is a translation initiation factor that binds to the cap structure and is part of a complex (eIF-4F) that promotes mRNA binding to ribosomes. Overexpression of eIF-4E in fibroblasts results in cell transformation.
What are the initiation factors involved in eukaryotic translation?
It requires at least 9 eukaryotic initiation factors (eIFs; Table 1) and comprises two steps: first, formation of 48S initiation complexes with established codon-anticodon base-pairing in the P-site of the 40S ribosomal subunits, and second, joining of 48S complexes with 60S subunits.
What is the major function of the eukaryotic initiation factor 4E eIF4E during cellular translation?
Eukaryotic initiation factor 4E (eIF4E), a fundamental effector and rate limiting element of protein synthesis, binds the 7-methylguanosine cap at the 5′ end of eukaryotic messenger RNA (mRNA) specifically as a constituent of eIF4F translation initiation complex thus facilitating the recruitment of mRNA to the …
What does poly A binding protein do?
Poly(A)-binding protein (PAB or PABP) is a RNA-binding protein which triggers the binding of eukaryotic initiation factor 4 complex (eIF4G) directly to the poly(A) tail of mRNA which is 200-250 nucleotides long.
Which eukaryotic initiation factor binds the 30S ribosome?
During the initiation stage of protein synthesis, the 30S ribosomal subunit binds the mRNA and the initiator tRNA (formyl-methionine-tRNAfMet) with the help of initiation factors 1, 2, and 3 (IF1, IF2, and IF3) (reviewed in Boelens and Gualerzi, 2002).
What is eukaryotes initiation?
Translation initiation in eukaryotes is a complex and highly regulated process requiring the action of at least 12 protein factors. The pathway is distinguished by the formation of a pre-initiation complex that recruits the 5′ end of the mRNA and scans along it to locate the start codon.
How many initiation factors are in eukaryotes?
In eukaryotes, at least eleven different initiation factors are required to properly initiate translation. Collectively, they ensure that the methionyl-initiator tRNA (Met-tRNAiMet) is brought in the P site of the ribosome to the initiator AUG of an mRNA.
What phosphorylates eIF4E?
eIF4E is phosphorylated by the MNK1/2 serine/threonine kinases, which are activated in response to mitogenic and stress signaling downstream of ERK1/2 and p38 MAP kinase, respectively (9, 10). eIF4E phosphorylation at serine 209 by MNK1/2 promotes its transformation activity (11, 12).
What is poly A tract?
poly(dT) tracts (poly(A) tracts), regions of DNA containing at least 20 contiguous dA residues on one strand and dT residues on the complementary strand, are found in about 2 X 10(4) copies interspersed throughout the human genome.
Is protein a polymer of amino acids?
Proteins are linear polymers formed by linking the α-carboxyl group of one amino acid to the α-amino group of another amino acid with a peptide bond (also called an amide bond). The formation of a dipeptide from two amino acids is accompanied by the loss of a water molecule (Figure 3.18).
What is the role of eIF4E in protein synthesis?
Almost all cellular mRNA require eIF4E in order to be translated into protein. The eIF4E polypeptide is the rate-limiting component of the eukaryotic translation apparatus and is involved in the mRNA-ribosome binding step of eukaryotic protein synthesis.
Which is site of phosphorylation of eukaryotic initiation factor 4E?
“Phosphorylation site of eukaryotic initiation factor 4E.” Cited for: PHOSPHORYLATION. “Serine 209, not serine 53, is the major site of phosphorylation in initiation factor eIF-4E in serum-treated Chinese hamster ovary cells.”
How is eIF4E a potential target for transcriptional control?
Both viruses and cellular proteins achieve this through an internal ribosome entry site in the RNA. Since eIF4E is an initiation factor that is relatively low in abundance, eIF4E is a potential target for transcriptional control.
Which is a repressor of translation initiation factor 4E?
Repressor of translation initiation that regulates EIF4E activity by preventing its assembly into the eIF4F complex: hypophosphorylated form competes with EIF4G1/EIF4G3 and strongly binds to EIF4E, leading to repress translation.