MRNA structure

That is transcription. Now, we get on with the final step the translation of mRNA structure into protein structure. 

In eukaryotes, mRNAs are initially transcribed as heterogeneous nuclear RNA, which still contains intervening sequences of the gene and must undergo processing to attain the final mRNA structure. 

Fig. 26. Nucleic acid structures. A The structure of the four bases in DNA, guanine (G), cytosine (C) adenine (A) and thymine (T). Uracil (U) replaces thymine (T) in RNA. B The spontaneous attraction of A for T and C for G allows the recognition of homologous sequences in aqueous solutions and the strong and specific hybridization of one sequence with its homologous sequence. C DNA forms a double helix at body temperature, which can be denatured to separate the strands by heating. D single stranded mRNA structure.

Simplified diagram of mRNA structure, (a) Typical eukaryotic mRNA. An AUG start codon is located near the 5 end of the mRNA. The single reading frame ends with one of the three trinucleotide sequences that represents a stop codon. Frequently, but not always, the 5 end of the mRNA is capped, and the 3 end contains a poly(A) tail. The cap structure is described in figure 28.17. 

Exclusion of (2) Design of S , 3 UTRs of mRNA Structural biology the inhibitors (3) PCR based system... 

Kozak M (2005), Regulation of translation via mRNA structure in prokaryotes and eukaryotes, Gene 361 13-37. 

Question What features of mRNA structure enable interaction with the 30S subunit ... 

The list of examples detailed above is by no means exhaustive. Several additional examples of the structure-based control of translation, such as repressor protein binding sequences on the mRNA transcripts and ribozymes [39], are among others that could be listed. The intentions of this chapter are not to enumerate examples of how structural characteristics of mRNA influence its translation. What should be evident from the preceding discussion is that mRNA structure is a critical determinant of translation, and synthetic DNA technology offers the possibility to alter and probe the effects of mRNA sequence on its structure and the resulting translation efficiency. Further developments in this area will be immensely valuable to metabolic engineering as it will enable practitioners to fine-tune the fluxes of desired metabolic pathways through modulation of protein levels. 

Gredell J, Berger A, Walton S (2008) Impact of target mRNA structure on siRNA silencing efficiency a large-scale study. Biotechnol Bioeng 100 744—755... 

Winkler WC, Nahvi A, Sudarsan N, Barrick JE, Breaker RR. An mRNA structure that controls gene expression by binding S-adenosylmethionine. Nat. Struct. Biol. 2003 10 701-707. Montange RK, Batey RT. Structure of the S-adenosylmethionine riboswitch regulatory mRNA element. Nature 2006 441 1172-1175. 

Higuchi H, Yang HY, Sabol SL. Rat neuropeptide Y precursor gene expression. mRNA structure, tissue distribution, and regulation by glucocorticoids, cyclic AMP, and phorbol ester. J. Biol. Chem. 1988 263 6288-6295. 

In summary, the codon TGA, which normally codes for termination of protein synthesis is programmed from a distance to encode the 21st amino acid selenocysteine a special tRNA is loaded in a unique and unorthodox way, incorporating a selenocysteine residue which is synthesised de novo at the tRNA level by special enzymes highly specialised proteins are required to recognise and bind the secondary mRNA structures and the tRNA specialised elongation factors have to compete with canonical ones and with release factors. No wonder that chemists and biochemists ask what are the unique properties of selenocysteine compared to cysteine (Amer, 2010) to justify the involvement of so many molecular partners (Allmang, Wurth, Krol, 2009). 

Viral as well as eucaryotlc mRNA structures have been intensely scrutinized (see Review 34). Virtually all mRNA molecules contain a "cap" structure at their 5 termini (Figure 1). 

Describe how eukaryotic mRNA structure can affect translational control. 

Gryczan, T., Grandi, G., Hahn, J., Grandi, R., and Dubnau, D. (1980). Conformational alteration of mRNA structure and the posttranscriptional regulation of erythromycin-induced drug... 

See also Structure of Prokaryotic mRNAs, Structure of tRNAs, Ribosomes, Initiation of Translation, Elongation of Translation, Termination of Translation... 

Bairn, S.B. and Sherman, F. (1988) mRNA structures influencing translation in the yeast Saccharomyces cerevisiae, MoL Cell, Biol, 8 (4), 1591-1601. 

The characteristics of the final gene may be analyzed using the Backtranslation Summary Report accessed from the Reports menu. Details on the final codon usage, mRNA structure, repeat sequences, and other features can be viewed. 

Darnell, J. E., 1976, mRNA structure and function. Prog. Nucl. Acid Res. Mol. Biol. 19 493. 

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