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EIF4G
Eukaryotic translation initiation factor 4 G (eIF4G) is a protein involved in eukaryotic translation initiation and is a component of the eIF4F cap-binding complex. Orthologs of eIF4G have been studied in multiple species, including humans, yeast, and wheat. However, eIF4G is exclusively found in domain Eukarya, and not in domains Bacteria or Archaea, which do not have capped mRNA. As such, eIF4G structure and function may vary between species, although the human EIF4G1 has been the focus of extensive studies. (Other human paralogs are EIF4G2 and EIF4G3.) Across species, eIF4G strongly associates with eIF4E, the protein that directly binds the mRNA cap. Together with the RNA helicase protein eIF4A, these form the eIF4F complex. Within the cell eIF4G is found primarily in the cytoplasm, usually bound to eIF4E; however, it is also found in the nucleus, where its function is unknown. It may have a role in nonsense-mediated decay. History eIF4G stands for eukaryotic initiation fac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4G3
Eukaryotic translation initiation factor 4 gamma 3 is a protein that in humans is encoded by the ''EIF4G3'' gene. The gene encodes a protein that functions in translation by aiding the assembly of the ribosome onto the messenger RNA template. Confusingly, this protein is usually referred to as eIF4GII, as although EIF4G3 is the third gene that is similar to eukaryotic translation initiation factor 4 gamma, the second isoform EIF4G2 is not an active translation initiation factor. Interactions EIF4G3 has been shown to interact with PABPC1 Polyadenylate-binding protein 1 is a protein that in humans is encoded by the ''PABPC1'' gene. The protein PABP1 binds mRNA and facilitates a variety of functions such as transport into and out of the nucleus, degradation, translation, and stabili .... References Further reading * * * * * * * * * * * * * * * {{gene-1-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4G1
Eukaryotic translation initiation factor 4 gamma 1 is a protein that in humans is encoded by the ''EIF4G1'' gene. Function The protein encoded by this gene is a component of the protein complex eIF4F, which is involved in the recognition of the mRNA cap, ATP-dependent unwinding of 5'-terminal secondary structure, and recruitment of mRNA to the ribosome. Alternative splicing results in five transcript variants encoding four distinct isoforms. eIF4G serves as a scaffold, interacting with mRNA and the other components of the eIF4F complex, as well as the PABP and eIF3. Interactions Eukaryotic translation initiation factor 4 gamma has been shown to interact with MKNK1, EIF4A1, EIF4E, MKNK2 and PABPC1. See also *Eukaryotic initiation factor Eukaryotic initiation factors (eIFs) are Protein, proteins or Protein complex, protein complexes involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of ribosomal preinitiation complexes ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4G2
Eukaryotic translation initiation factor 4 gamma 2 (also called p97, NAT1, and DAP-5) is a protein that in humans is encoded by the ''EIF4G2'' gene. Function Translation initiation is mediated by specific recognition of the cap structure by eukaryotic translation initiation factor 4F (eIF4F), which is a cap binding protein complex that consists of three subunits: eIF4A, eIF4E and eIF4G. The protein encoded by the eIF4G2 gene shares similarity with the C-terminal region of eIF4G1 that contains the binding sites for eIF4A and eIF3. eIF4G2 additionally contains a binding site for eIF4E at the N-terminus. Unlike eIF4G1, which supports cap-dependent and independent translation, the eIF4G2 gene product functions as a general repressor of translation by forming translationally inactive complexes. In vitro and in vivo studies indicate that translation of this mRNA initiates exclusively at a non-AUG (GUG) codon. Alternatively spliced transcript variants encoding different isoforms of this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internal Ribosome Entry Site
An internal ribosome entry site, abbreviated IRES, is an RNA element that allows for translation initiation in a cap-independent manner, as part of the greater process of protein synthesis. In eukaryotic translation, initiation typically occurs at the 5' end of mRNA molecules, since 5' cap recognition is required for the assembly of the initiation complex. The location for IRES elements is often in the 5'UTR, but can also occur elsewhere in mRNAs. History IRES sequences were first discovered in 1988 in the poliovirus (PV) and encephalomyocarditis virus (EMCV) RNA genomes in the labs of Nahum Sonenberg and Eckard Wimmer, respectively. They are described as distinct regions of RNA molecules that are able to recruit the eukaryotic ribosome to the mRNA. This process is also known as cap-independent translation. It has been shown that IRES elements have a distinct secondary or even tertiary structure, but similar structural features at the levels of either primary or secondary structur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PABPI
Polyadenylate-binding protein 1 is a protein that in humans is encoded by the ''PABPC1'' gene. The protein PABP1 binds mRNA and facilitates a variety of functions such as transport into and out of the nucleus, degradation, translation, and stability. There are two separate PABP1 proteins, one which is located in the nucleus (PABPN1) and the other which is found in the cytoplasm (PABPC1). The location of PABP1 affects the role of that protein and its function with RNA. Function The poly(A)-binding protein (PAB or PABP), which is found complexed to the 3' poly(A) tail of eukaryotic mRNA, is required for poly(A) lengthening and the termination of translation. In humans, the PABPs comprise a small nuclear isoform and a conserved gene family of other poly(A)-binding proteins. upplied by OMIMref name="entrez"> PABPC1 is usually diffused within the cytoplasm and concentrated at sites of high mRNA concentration such as stress granules, processing bodies, and locations of high translat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4E
Eukaryotic translation initiation factor 4E, also known as eIF4E, is a protein that in humans is encoded by the ''EIF4E'' gene. Structure and function Most eukaryotic cellular mRNAs are blocked at their 5'-ends with the 7-methyl-guanosine five-prime cap structure, m7GpppX (where X is any nucleotide). This structure is involved in several cellular processes including enhanced translational efficiency, splicing, mRNA stability, and RNA nuclear export. 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. 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. The other subunits of eIF4F are a 47-kD polypeptide, terme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryotic Initiation Factor 4F
Eukaryotic initiation factor 4F (eIF4F) is a heterotrimeric protein complex that binds the 5' cap of messenger RNAs (mRNAs) to promote eukaryotic translation initiation. The eIF4F complex is composed of three non-identical subunits: the DEAD-box RNA helicase eIF4A, the cap-binding protein eIF4E, and the large "scaffold" protein eIF4G. The mammalian eIF4F complex was first described in 1983, and has been a major area of study into the molecular mechanisms of cap-dependent translation initiation ever since. Function eIF4F is important for recruiting the small ribosomal subunit (40S) to the 5' cap of mRNAs during cap-dependent translation initiation. Components of the complex are also involved in cap-independent translation initiation; for instance, certain viral proteases cleave eIF4G to remove the eIF4E-binding region, thus inhibiting cap-dependent translation. Structure Structures of eIF4F components have been solved individually and as partial complexes by a variety ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4F
Eukaryotic initiation factor 4F (eIF4F) is a heterotrimeric protein complex that binds the 5' cap of messenger RNAs (mRNAs) to promote eukaryotic translation initiation. The eIF4F complex is composed of three non-identical subunits: the DEAD-box RNA helicase eIF4A, the cap-binding protein eIF4E, and the large "scaffold" protein eIF4G. The mammalian eIF4F complex was first described in 1983, and has been a major area of study into the molecular mechanisms of cap-dependent translation initiation ever since. Function eIF4F is important for recruiting the small ribosomal subunit (40S) to the 5' cap of mRNAs during cap-dependent translation initiation. Components of the complex are also involved in cap-independent translation initiation; for instance, certain viral proteases cleave eIF4G to remove the eIF4E-binding region, thus inhibiting cap-dependent translation. Structure Structures of eIF4F components have been solved individually and as partial complexes by a variety ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryotic Translation
Eukaryotic translation is the biological process by which messenger RNA is translated into proteins in eukaryotes. It consists of four phases: gene translation, elongation, termination, and recapping. Initiation Translation initiation is the process by which the ribosome and its associated factors bind to an mRNA and are assembled at the start codon. This process is defined as either cap-dependent, in which the ribosome binds initially at the 5' cap and then travels to the stop codon, or as cap-independent, where the ribosome does not initially bind the 5' cap. Cap-dependent initiation Initiation of translation usually involves the interaction of certain key proteins, the initiation factors, with a special tag bound to the 5'-end of an mRNA molecule, the 5' cap, as well as with the 5' UTR. These proteins bind the small (40S) ribosomal subunit and hold the mRNA in place. eIF3 is associated with the 40S ribosomal subunit and plays a role in keeping the large (60S) ribosomal sub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Luteovirus Cap-independent Translation Element
The Barley yellow dwarf virus-like cap-independent translation element (BTE) is an RNA element found in the 3' UTR of some luteoviruses. This element mediates translation of genomic RNA and subgenomic RNA1 (sgRNA1). BTEs have a consensus sequence, GGAUCCUGGGAAACAGG, embedded in series of three to six stem-loops that radiate from a central hub. BTE has been found to bind to eIF4G and weakly to eIF4E (proteins involved in translation initiation). BTE allows translation initiation of an mRNA without a 7mG cap (required for translation in most eukaryotic mRNA). Other forms of cap-independent translation elements (CITE) exist (primarily in plant viruses from the Luteovirus, Necrovirus, Dianthovirus and Umbravirus genera of plantviruses, but also in some host mRNA; notably many heat shock mRNA lack a 7mG cap but are still translated). The general purpose of BTE and these other CITE's is to get the ribosome to begin translation without the 7mG cap. In the case of BTE it "tricks" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryotic Small Ribosomal Subunit (40S)
The eukaryotic small ribosomal subunit (40S) is the smaller subunit of the eukaryotic 80S ribosomes, with the other major component being the large ribosomal subunit (60S). The "40S" and "60S" names originate from the convention that ribosomal particles are denoted according to their sedimentation coefficients in Svedberg units. It is structurally and functionally related to the 30S subunit of 70S prokaryotic ribosomes. However, the 40S subunit is much larger than the prokaryotic 30S subunit and contains many additional protein segments, as well as rRNA expansion segments. Function The 40S subunit contains the decoding center which monitors the complementarity of tRNA and mRNA in protein translation. It is the largest component of several translation initiation complexes, including the 43S and 48S preinitiation complexes (PICs), being bound by several eukaryotic initiation factors, including eIF1, eIF1A, and eIF3. The 40S ribosomal subunit is also tightly bound by the HCV IRES ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribosome Shunting
Ribosome shunting is a mechanism of translation initiation in which ribosomes bypass, or "shunt over", parts of the 5' untranslated region to reach the start codon. However, a benefit of ribosomal shunting is that it can translate backwards allowing more information to be stored than usual in an mRNA molecule. Some viral RNAs have been shown to use ribosome shunting as a more efficient form of translation during certain stages of viral life cycle or when translation initiation factors are scarce (e.g. cleavage by viral proteases). Some viruses known to use this mechanism include adenovirus, Sendai virus, human papillomavirus, duck hepatitis B pararetrovirus, rice tungro bacilliform viruses, and cauliflower mosaic virus Cauliflower mosaic virus (CaMV) is a member of the genus ''Caulimovirus'', one of the six genera in the family ''Caulimoviridae'', which are pararetroviruses that infect plants. Pararetroviruses replicate through reverse transcription just lik .... In these vir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
