Eukaryotes mRNA structure

Describe how eukaryotic mRNA structure can affect translational control. 

Kozak M Structural features in eukaryotic mRNAs that modulate the initiation of translation. J Biol Chem 1991 266 1986. 

Figure 39-19. Structure of a typical eukaryotic mRNA showing elements that are involved in regulating mRNA stability. The typical eukaryotic mRNA has a 5 noncoding sequence (5 NCS), a coding region, and a 3 NCS. All are capped at the 5 end, and most have a polyadenylate sequence at the 3 end. The 5 cap and 3 poly(A) tail protect the mRNA against exonuclease attack. Stem-loop structures in the 5 and 3 NCS, features in the coding sequence, and the AU-rich region in the 3 NCS are thought to play roles in mRNA stability.

Figure 7.4 (a) IREs in eukaryotic mRNAs the secondary structures of ferritin and transferrin receptor IREs. (b) The IRE localization in mRNAs the translation/ribosome binding element in the 5 -UTR of ferritin mRNA is above, that of the stability/ turnover element in the 3 -UTR of transferrin receptor mRNA is below. Adapted from Theil, 1998, by courtesy of Marcel Dekker, Inc. 

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. 

Initiation The components of the translation system are assembled, and mRNA associates with the small ribosomal subunit. The process requires initiation factors. In prokaryotes,a purine-rich region (the Shine-Dalgarno sequence) of the mRNA base-pairs with a complementary sequence on 16S rRNA, resulting in the positioning of the mRNA so that translation can begin. The 5 -cap on eukaryotic mRNA is used to position that structure on the ribosome. The initiation codon is 5 -AUG-3. ... 

Structure of the 5 methylated cap of eukaryotic mRNA. A 7-methylguanosine (in red) is attached through a triphosphate linkage formed between its 5 -OH and the 5 -OH of the terminal residue in... 

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. 

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

Maruyama, K. and Sugano, S. (1994) Oligo-capping a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides. Gene 138,171-174. 

What major structural requirement for initiation of translation of eukaryotic mRNA docs not exist for bacterial mRNA ... 

Figure 23-7 Structure of 7-methyl-guanosine capped eukaryotic mRNA. (From Stryer, L. (1988) Biochemistry,...

Structures of prokaryotic and eukaryotic primary transcripts (mRNAs). Prokaryotic mRNAs are polygenic, do not contain introns or exons, and are short lived in the cell. Eukaryotic mRNAs are monogenic, contain introns and exons, and usually are long lived in the cell. 

A FIGURE 4-13 Structure of the 5 methylated cap of eukaryotic mRNA. The distinguishing chemicai features are the 5 5 iinkage of 7-methyiguanyiate to the initiai nucieotide of the mRNA moiecuie and the methyi group on the 2 hydroxyi of the ribose of the first nucieotide (base 1). Both these features occur in aii animai ceiis and in ceiis of higher piants yeasts iack the methyi group on nucieotide 1. The ribose of the second nucieotide (base 2) aiso is methyiated in vertebrates. [See A. J. Shatkin, 1976, Ce//9 645.]... 

A EXPERIMENTAL FIGURE 4-30 Eukaryotic mRNA forms a circular structure owing to interactions of three proteins. 

In the presence of purified poly(A)-binding protein I (PABPI), elF4E, and elF4G, eukaryotic mRNAs form circular structures, visible in this force-field electron micrograph. In these structures, protein-protein and protein-mRNA interactions form a bridge between the 5 and 3 ends of the mRNA as diagrammed in Figure 4-31. [Courtesy of A. Sachs.]... 

What are the major differences in the synthesis and structure of prokaryotic and eukaryotic mRNAs ... 

Capping of eukaryotic mRNA. (a) Enzymatic reactions required for 50 capping SAM is -S -adenosyl methionine and SAC is -S -adenosyl homocysteine, (b) Structure of 7-methylguanosine cap. 

Merrik, W. C. (1990). Eukaryotic mRNAs Strange solutions require unusual problems. In The Ribosome—Structure, Function, and Evolution (W. E. Hill, A. Dahlberg, R. A. Garrett, P. B. Moore D. Schlessinger, and J. R. Warner, Eds.), pp. 203-214. American Society for Microbiology, Washington, DC. 

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