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The ribosome can localize to the start site by direct binding, initiation factors, and/or ITAFs (IRES trans-acting factors) bypassing the need to scan the entire 5' UTR. This method of translation is important in conditions that require the translation of specific mRNAs during cellular stress, when overall translation is reduced.
Through several studies Marilyn Kozak was the first to recognize the main role of scanning during initiation of translation in mammalian cells. The AUG codon in mammals is optimally recognized by the context GCCRCCAUGG, also known as a “Kozak Consensus Sequence.” [5] Purine (R) and each of the nucleotides within this sequence are highly conserved and provide an important function in ...
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.
Translation in plants is tightly regulated as in animals, however, it is not as well understood as transcriptional regulation. There are several levels of regulation including translation initiation, mRNA turnover and ribosome loading. Recent studies have shown that translation is also under the control of the circadian clock.
There is also evidence that a G in the -6 position is important in the initiation of translation. [4] While the +4 and the −3 positions in the Kozak sequence have the greatest relative importance in the establishing a favorable initiation context a CC or AA motif at −2 and −1 were found to be important in the initiation of translation in ...
Eukaryotic initiation factors (eIFs) are proteins or protein complexes involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of ribosomal preinitiation complexes around the start codon and are an important input for post-transcription gene regulation .
Cancer cells must frequently regulate the translation phase of gene expression, though it is not fully understood why translation is targeted over steps like transcrion. While cancer cells often have genetically altered translation factors, it is much more common for cancer cells to modify the levels of existing translation factors. [ 23 ]
The formation of the eukaryotic initiation complex. In cancerous cells, initiation factors assist in cellular transformation and development of tumors. The survival and growth of cancer is directly related to the modification of initiation factors and is used as a target for pharmaceuticals. Cells need increased energy when cancerous and derive ...