Translational regulation
Translational regulation refers to the
In prokaryotes
Initiation
Initiation of translation is regulated by the accessibility of ribosomes to the
Elongation
Due to the fact that translation elongation is an irreversible process, there are few known mechanisms of its regulation. However, it has been shown that translational efficiency is reduced via diminished tRNA pools, which are required for the elongation of polypeptides. In fact, the richness of these tRNA pools are susceptible to change through cellular oxygen supply.[7]
Termination
The termination of translation requires coordination between release factor proteins, the mRNA sequence, and ribosomes. Once a termination codon is read, release factors RF-1, RF-2, and RF-3 contribute to the hydrolysis of the growing polypeptide, which terminates the chain. Bases downstream the stop codon affect the activity of these release factors. In fact, some bases proximal to the stop codon suppress the efficiency of translation termination by reducing the enzymatic activity of the release factors. For instance, the termination efficiency of a UAAU stop codon is near 80% while the efficiency of UGAC as a termination signal is only 7%.[8]
In eukaryotes
Initiation
When comparing initiation in eukaryotes to prokaryotes, perhaps one of the first noticeable differences is the use of a larger 80S ribosome. Regulation of this process begins with the supply of methionine by a tRNA anticodon that basepairs AUG. This base pairing comes about by the scanning mechanism that ensues once the small 40S ribosomal subunit binds the
Elongation
The hallmark difference of elongation in eukaryotes in comparison to prokaryotes is its separation from transcription. While prokaryotes are able to undergo both cellular processes simultaneously, the spatial separation that is provided by the
Termination
Mechanistically, eukaryotic translation termination matches its prokaryotic counterpart. In this case, termination of the polypeptide chain is achieved through the
In plants
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. Like transcription, the translation state of numerous mRNAs changes over the diel cycle (day night period).[15]
References
- ISBN 978-0716771081.
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- ^ Milón P, Maracci C, Filonava L, Gualerzi CO, Rodnina MV. Real-time assembly landscape of bacterial 30S translation initiation complex. Nat Struct Mol Biol. 2012;19:609–615.
- ^ Poole, E. S., Brown, C. M., & Tate, W. P. (1995). The identity of the base following the stop codon determines the efficiency of in vivo translational termination in Escherichia coli. The EMBO Journal, 14(1), 151–158.
- PMID16238092.
- ^ Kimball S.R. Eukaryotic initiation factor eIF2. Int. J. Biochem. Cell Biol. 1999;31:25–29.
- ^ Ovchinnikov LP, Motuz LP, Natapov PG, Averbuch LJ, Wettenhall RE, Szyszka R, Kramer G, Hardesty B. 1990. Three phosphorylation sites in elongation factor 2. FEBS Lett. 275: 209– 212
- ^ Horman S, Browne G, Krause U, Patel J, Vertommen D, Bertrand L, Lavoinne A, Hue L, Proud C, Rider M. 2002. Activation of AMP-activated protein kinase leads to the phosphorylation of elongation factor 2 and an inhibition of protein synthesis. Curr. Biol. 12: 1419– 1423
- ^ Dabrowski M, Bukowy-Bieryllo Z, Zietkiewicz E. Translational readthrough potential of natural termination codons in eucaryotes - the impact of RNA sequence. RNA Biol. 2015;12:950–8.
- PMID26392078.