Translational machinery

RNA structures, compared to the helical motifs that dominate DNA, are quite diverse, assuming various loop conformations in addition to helical structures. This diversity allows RNA molecules to assume a wide variety of tertiary structures with many biological functions beyond the storage and propagation of the genetic code. Examples include transfer RNA, which is involved in the translation of mRNA into proteins, the RNA components of ribosomes, the translation machinery, and catalytic RNA molecules. In addition, it is now known that secondary and tertiary elements of mRNA can act to regulate the translation of its own primary sequence. Such diversity makes RNA a prime area for the study of structure-function relationships to which computational approaches can make a significant contribution. 

Biological systems depend on specific detailed recognition of molecules that distinguish between chiral forms. The translation machinery for protein synthesis has evolved to utilize only one of the chiral forms of amino acids, the L-form. All amino acids that occur in proteins therefore have the L-form. There is, however, no obvious reason why the L-form was chosen during evolution and not the D-form... 

The human HS cycle can be considered broadly as a period which leads to the dramatic shift in activities of the transcriptional and translational machinery followed by eventual recovery and resumption of original activities preceding stress. Figure 1 depicts many of the key events in the HS cycle for a typical human cell line such as cervical carcinoma-derived HeLa cells. Most cells respond in an identical fashion, but some cell types that have distinctive HS responses. These differences are manifested by shifts in the relative concentrations of accumulated HS proteins and possibly in the pattern of posttranslational modifications. In all cases, however, the cellular stress response is heralded by induction of a specific transcription factor whose DNA binding activity facilitates increased expression of one or more of the stress-inducible genes. 

Comment It is critical to remove excess cap analogue from in vitro transcribed transcripts prior to transfection, because the cap analogue will compete with transcripts for the cellular translational machinery. Also, even after DNase treatment, the RNA sample may still contain traces of functional pDNA, which may interfere with subsequent detection by RT-PCR. Furthermore, plasmids containing a mammalian promoter may even give rise to de novo transcription in transfected cells. 

Both the overall rate of protein synthesis and the translation of certain specific mRNAs are controlled by agents such as hormones, growth factors, and other extracellular stimuli. As precursors for protein assembly, amino acids also regulate the translational machinery. Because protein synthesis consumes a high proportion of cellular metabolic energy, the energy status of the cell also modulates translation factors. 

Studies have shown that plants can make biologically active recombinant proteins through both transgenic and transient expression approaches. Although the plant post-translational machinery is similar to that of mammalian cells, there are some notable differences, e.g. differences in glycosylation, particularly the absence of sia-lation, which may impact the activity of certain proteins. The absence of mammalian enzymes may prevent complex maturation processes that are critical for the biological activity of proteins such as insulin. Fortunately these shortcomings affect the activity of only a limited number of proteins. 

There is no doubt that plants represent one of the most productive and yet inexpensive sources of biomass. The absence of contaminating animal pathogens, the eukaryotic translational machinery and the ease of plant virus manipulation make plants... 

Recent studies have shown that proteins interacting with the release factors can modulate the efficiency of stop codon readthrough. Physical and functional interaction with the translation termination factors was demonstrated for different components of the translational machinery. 

Aminoglycoside effects on mutants without direct connection to the translation machinery... 

Nelson RJ, Ziegelhoffer T, Nicolet C, Werner-Washburne M, Craig EA (1992) The translation machinery and 70 kd heat shock protein cooperate in protein synthesis. Cell 71 97-105 Nissen P, Hansen J, Ban N, Moore PB, Steitz TA (2000) The structural basis of ribosome activity in peptide bond synthesis. Science 289 920-930... 

---