Eukaryotic Translation Initiation Factor

EIF5A2 is part of the eukaryotic initiation factor 5A subfamily, is an vital protein strongly linked to cellular polyamine homeostasis. EIF5A2 promotes the formation of the first peptide bond during the initial stage of protein synthesis. EIF5A2 is the single eukaryotic protein to have a hypusine residue, which is a post-translational modification of a lysine by the addition of a butylamino group.

EIF5A is the single protein identified to contain remarkable amino acid formed by the action of deoxyhypusine synthase and deoxyhypusine hydroxylase using spermidine as the substrate. EIF5A takes part in the first step of peptide bond formation in translation, nevertheless further experiments implicates it as a universally conserved translation elongation factor. Modulation of EIF5A is connected to proliferation and cancer. Expression of EIF-5A is upregulated in the PBMCs of HIV-1 patients. EIF5A coordinates significant cellular processes like cell viability and senescence during its effects on the stability of certain mRNAs. Heat stress-induced loss of EIF-5A in a human pancreatic cancer cell line. EIF5A stability takes part in determining the fate of the particular cell type after severe heat stress.

Eukaryotic translation initiation factor 4H (EIF4H) is a 248 amino acid protein which localizes to the perinuclear region of the cytoplasm and is expressed as 2 isoforms, termed short and long. EIF4H functions to stimulate the initiation of protein synthesis at the level of mRNA employment. EIF4H stimulates the RNA-dependent ATP hydrolysis catalyzed by EIF4A and EIF4B. EIF4H gene defects linked to Williams- Beuren syndrome (WBS), a rare developmental disorder characterized by cardiovascular and musculo-skeletal abnormalities and caused by the deletion of contiguous genes at 7q11.23.

Eukaryotic Translation Initiation Factor 4E-Binding Protein 3 (EIF4EBP3) belongs to the EIF4EBP family whose proteins bind to eukaryotic initiation factor 4E and regulate its assembly into EIF4F, the multi-subunit translation initiation factor that identifies the mRNA cap structure.

EIF4EBP2 belongs to the eukaryotic translation initiation factor 4E binding protein family. Even though EIF4EBP2 protein binds eIF4E and inhibits translation initiation, growth factors can release this inhibition by a phosphorylation-dependent disruption. EIF4EBP2 mediates the regulation of protein translation by hormones, growth factors and other stimuli that signal through the MAP kinase pathway. Regulation of this protein is associated to cell proliferation, cell differentiation and viral infection.

EIF4EBP1 (eukaryotic translation initiation factor 4E-binding protein 1) belongs to a family of translation repressor proteins. EIF4EBP1 regulates eIF4E (eukaryotic translation initiation factor 4E) activity by preventing its assembly into the eIF4F complex and mediates the regulation of protein translation by hormones, growth factors and other stimuli that signal through the MAP kinase and mTORC1 pathways. EIF4EBP1 is phosphorylated in response to various signals including UV irradiation, resulting in its dissociation from eIF4E and activation of mRNA translation. EIF4EBP1 C-terminus has domains which control function and phosphorylation. EIF4EBP1 has a role in progression of breast neoplasms through cell signaling.

EIF4E is part of the eukaryotic initiation factor 4 families, controls translation of maternal mRNAs in early embryos before the onset of zygotic transcription. EIF4E identifies and binds to the 7 methyl GTP cap structure of eukaryotic mRNAs, thus modulates the initiation of translation. EIF4E enables ribosome binding by inducing the unwinding of the mRNAs secondary structures.

EIF4E is part of the eukaryotic initiation factor 4 families, controls translation of maternal mRNAs in early embryos before the onset of zygotic transcription. EIF4E identifies and binds to the 7 methyl GTP cap structure of eukaryotic mRNAs, thus modulates the initiation of translation. EIF4E enables ribosome binding by inducing the unwinding of the mRNAs secondary structures.

Eukaryotic initiation factor 4A-III (EIF4A3) is a member of the DEAD box helicase family and eIF4A subfamily. DEAD box proteins, distinguished by the conserved motif Asp-Glu-Ala-Asp (DEAD), are putative RNA helicases. These proteins are involved in several cellular processes including alteration of RNA secondary structure, such as translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly. EIF4A3 is a part of a splicing-dependent multiprotein exon junction complex (EJC) accumulated at splice junction on mRNAs. Based upon their distribution patterns, some members of the DEAD box helicase family are thought to be involved in embryogenesis, spermatogenesis, and cellular growth and division.

EIF3K is a member of the eIF3 subunit K family. EIF3K is the smallest subunit of eIF3 and it interacts with a number of other subunits of eIF3 and the 40S ribosomal subunit. EIF3K is conserved among high eukaryotes, including mammals, insects, and plants, and it is universally expressed in human tissues. EIF3K is distributed both in nucleus and cytoplasm and colocalized with cyclin D3, a regulatory subunit of cyclin-dependent kinase 4 (Cdk4).

Eukaryotic translation initiation factor 3 subunit J (EIF3J) is a member of the EIF-3 subunit J family. EIF3 has a crucial role in binding of initiator methionyl-tRNA and mRNA to the 40S ribosomal subunit to produce the 40S initiation complex. EIF3J binds to the aminoacyl (A) site and mRNA access channel of the 40S subunit, setting EIF3J directly in the ribosomal decoding center. In addition, EIF3J interacts with eIF1A and reduces 40S subunit affinity for mRNA. An elevated affinity for mRNA is restored upon enlistment of initiator tRNA, despite the fact EIF3J remains in the mRNA-binding cleft in the presence of tRNA.

Eukaryotic translation initiation factor 3, subunit I (EIF3I) is part of the eukaryotic translation initiation factor 3 (eIF-3) complex, which is essential for numerous steps in the initiation of protein synthesis. The eIF-3 complex links with the 40S ribosome and facilitates the recruitment of eIF-1, eIF-1A, eIF-2: GTP: methionyl-tRNAi and eIF-5 to form the 43S pre-initiation complex (43S PIC). The eIF-3 complex stimulates mRNA recruitment to the 43S PIC and scanning of the mRNA for AUG recognition. The eIF-3 complex is also essential for disassembly and recycling of post-termination ribosomal complexes and subsequently prevents premature joining of the 40S and 60S ribosomal subunits prior to initiation. Among the diseases associated with EIF3I are clonorchiasis, and tonsillitis.

Eukaryotic translation initiation factor 3, subunit I (EIF3I) is part of the eukaryotic translation initiation factor 3 (eIF-3) complex, which is essential for numerous steps in the initiation of protein synthesis. The eIF-3 complex links with the 40S ribosome and facilitates the recruitment of eIF-1, eIF-1A, eIF-2: GTP: methionyl-tRNAi and eIF-5 to form the 43S pre-initiation complex (43S PIC). The eIF-3 complex stimulates mRNA recruitment to the 43S PIC and scanning of the mRNA for AUG recognition. The eIF-3 complex is also essential for disassembly and recycling of post-termination ribosomal complexes and subsequently prevents premature joining of the 40S and 60S ribosomal subunits prior to initiation. Among the diseases associated with EIF3I are clonorchiasis, and tonsillitis.

Eukaryotic Translation Initiation Factor 3F, also known as EIF3F belongs to the eIF-3 subunit F family. EIF3F is a component of the eukaryotic translation initiation factor 3 (eIF-3) complex, which isessential for several steps in the initiation of protein synthesis. The eIF-3 complex associates with the 40S ribosomeand facilitates the recruitment of eIF-1, eIF-1A, eIF 2: GTP: methionyl-tRNAi and eIF-5 to form the 43S preinitiationcomplex (43S PIC). In addition, the eIF-3 complex stimulates mRNA recruitment to the 43S PIC and scanning of the mRNA forAUG recognition. The eIF-3 complex is also necessary for disassembly and recycling of post termination ribosomalcomplexes and subsequently prevents premature union of the 40S and 60S ribosomal subunits prior to initiation. Among the diseases associated with EIF3F are intrahepatic cholangiocarcinoma, and cholangiocarcinoma.

EIF2S1 participates in the premature steps of protein synthesis by forming a ternary complex with GTP and initiator tRNA which binds to a 40S ribosomal subunit, followed by mRNA binding to create a 43S pre-initiation complex. Junction of the 60S ribosomal subunit to form the 80S initiation complex is preceded by hydrolysis of the GTP bound to eIF-2 and release of an eIF-2-GDP binary complex. In order for eIF-2 to recycle and catalyze another round of initiation, the GDP bound to eIF-2 should exchange with GTP by way of a reaction catalyzed by eIF-2B.

EIF2B1 is one of five subunits of eukaryotic translation initiation factor 2B (EIF2B), which is a GTP exchange factor for eukaryotic initiation factor 2 and an essential regulator for protein synthesis. Phosphorylation of eIF2 inhibits GEF activity of EIF2B, an inhibition which requires the eIF2B1 subunit. Defects in eIF2B1 are a cause of leukoencephalopathy with vanishing white matter (VWM), a brain disease which is characterized by head trauma and motor deterioration.

EIF1B is critical for the scanning process in vitro. EIF1B is an element of a complex involved in recognition of the initiator codon during the scanning process. Translation is also initiated by the function of EIF1B in regulating the activity of ribosomal subunits 43S, 48S and 40S. EIF1B enables 43S ribosomal complexes to distinguish between cognate and near-cognate initiation codons, perceiving the nucleotide content of initiation codons.

EIF1AY is comparable to eukaryotic translation initiation factor 1A (EIF1A). EIF1AY protein is essential for highest rate of protein biosynthesis. EIF1AY increases ribosome dissociation into subunits and is obligatory for the binding of the 43S complex (a 40S subunit, eIF2/GTP/Met-tRNAi and eIF3) to the 5' end of capped RNA.

EIF1AX is an important eukaryotic translation initiation factor. EIF1AX is essential for the binding of the 43S complex (a 40S subunit, eIF2/GTP/Met-tRNAi and eIF3) to the 5'' end of capped RNA. EIF1AP1 is needed for maximal rate of protein biosynthesis. EIF1AX increases ribosome dissociation into subunits and stabilizes the binding of the initiator Met-tRNA (I) to 40 S ribosomal subunits.

EIF1 is important for scanning and plays a role in initiation site selection. EIF1 promotes the assembly of 48S ribosomal at the authentic initiation codon of a conventional capped mRNA.

Eukaryotic elongation factor-2 kinase (EEF2K) is threonine kinase which regulates protein synthesis by means of controlling the rate of peptide chain elongation. Upon activation through a diversity of upstream kinases including AMPK or TRPM7, EEF2K phosphorylates the elongation factor EEF2 at a sole site, renders it unable to bind ribosomes and therefore inactive. In turn, the rate of protein synthesis is being reduced.

Eukaryotic Translation Elongation Factor 2 (EEF2) which is necessary factor for protein synthesis is a part of the GTP-binding translation elongation factor family. EEF2 catalyzes the GTP-dependent ribosomal translocation step during translation elongation. EEF2 is also catalyzes the coordinated movement of the mRNA as well as the 2 tRNA molecules and conformational changes in the ribosome. EF-2 kinase phosporylation inactivates the EEF2 protein.

Eukaryotic Translation Elongation Factor 1 Gamma (EEF1G) takes part in anchoring the complex to additional cellular components. EEF1G is a multi-protein complex which is in charge of the delivery of aminoacyl-tRNAs to the ribosome. Over expression of EEF1G is linked with pancreatic cancer, due to the role of EEF1G protein in the oncogenic transformation process.

Eukaryotic translation elongation factor 1 epsilon-1 (EEF1E1) shares sequence similarity with the amino-terminal ends of the Beta and Gamma subunits of EF-1. By specifically interacting with MetRS, EEF1E1 binds to a macromolecular tRNA synthtase complex which catalyzes the ligation of specific amino acids to their cognate tRNAs. Upon DNA damage, EEF1E1 translocates to the nucleus where it interacts with ATM and ATR, resulting in p53 activation.

Eukaryotic translation elongation factor 1 delta (EEF1D) is a subunit of the elongation factor-1 complex that is responsible for the enzymatic transport of aminoacyl tRNAs to the ribosome. EEF1D functions as guanine nucleotide exchange factor. EEF1D interacts with HIV-1 Tat, and consequently represses the translation of host-cell, but not HIV-1, mRNAs. EEF1D overexpression is linked to oesophageal carcinoma and may negatively influence the outcome of medulloblastomas.

Elongation factor 1-beta (EEF1B2) is a translation elongation factor. EEF1B2 is a guanine nucleotide exchange factor which is involved in the transfer of aminoacylated tRNAs to the ribosome. Both EEF1B2 and EEF1D stimulate the exchange of GDP bound to EEF1A to GTP.

EEF1A1 is an isoform of the alpha subunit of the elongation factor-1 complex, which is responsible forthe enzymatic release of aminoacyl tRNAs to the ribosome. EEF1A1 is expressed in brain, placenta, lung, liver, kidney, and pancreas, and the other isoform (alpha 2) is expressed in brain, heart and skeletal muscle. EEF1A1 is recognized as an autoantigen in 66% of patients with Felty syndrome. EEF1A1 has multiple copies on numerous chromosomes, part of them, if not all, symbolize different pseudogenes. Among the diseases associated with EEF1A1 are tinea nigra and andcervical cancer.

The Argonaute protein is part of the RISC or RNA-induced silencing complex, as so, the protein has a key part in the slicing processes of RNA. The RNA interference (RNAi) is being held by RISC. Small non-coding RNA fragments bond to the Argonaute proteins, through base pairing, eventually leads to the cleavage of messenger RNA or translation suppression.

The Argonaute protein is part of the RISC or RNA-induced silencing complex, as so, the protein has a key part in the slicing processes of RNA. The RNA interference (RNAi) is being held by RISC. Small non-coding RNA fragments bond to the Argonaute proteins, through base pairing, eventually leads to the cleavage of messenger RNA or translation suppression.