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Eukaryotic translation is the biological process by which messenger RNA is translated into proteins in eukaryotes. It consists of four phases: initiation, elongation, termination, and recapping. It consists of four phases: initiation, elongation, termination, and recapping.
The first step in initiation is formation of the pre-initiation complex, 48S PIC. The small ribosomal subunit and various eukaryotic initiation factors are recruited to the mRNA 5′ TL and to form the 48S PIC complex, which scans 5′ to 3′ along the mRNA transcript, inspecting each successive triplet for a functional start codon.
Overview of eukaryotic messenger RNA (mRNA) translation Translation of mRNA and ribosomal protein synthesis Initiation and elongation stages of translation involving RNA nucleobases, the ribosome, transfer RNA, and amino acids The three phases of translation: (1) in initiation, the small ribosomal subunit binds to the RNA strand and the initiator tRNA–amino acid complex binds to the start ...
Leaky scanning is a mechanism used during the initiation phase of eukaryotic translation that enables regulation of gene expression.During initiation, the small 40S ribosomal subunit (as a 43S PIC) "scans" or moves in a 5' --> 3' direction along the 5'UTR to locate a start codon to commence elongation.
The eIF2 alpha subunit is characterized by an OB-fold domain and two beta strands. This subunit helps to regulate translation, as it becomes phosphorylated to inhibit protein synthesis. [2] The eIF4F complex supports the cap-dependent translation initiation process and is composed of the initiation factors eIF4A, eIF4E, and eIF4G.
Initiation of eukaryotic translation nearly always occurs at and is dependent on the 5' cap of mRNA molecules, where the translation initiation complex forms and ribosomes engage the mRNA. IRES elements, however allow ribosomes to engage the mRNA and begin translation independently of the 5' cap.
Eukaryotic ribosomes are known to bind to transcripts in a mechanism unlike the one involving the 5' cap, at a sequence called the internal ribosome entry site. This process is not dependent on the full set of translation initiation factors (although this depends on the specific IRES) and is commonly found in the translation of viral mRNA. [9]
Translation promotes transcription elongation and regulates transcription termination. Functional coupling between transcription and translation is caused by direct physical interactions between the ribosome and RNA polymerase ("expressome complex"), ribosome-dependent changes to nascent mRNA secondary structure which affect RNA polymerase activity (e.g. "attenuation"), and ribosome-dependent ...