MRNA biosynthesis

Metabolism of Macromolecules mRNA biosynthesis (bacteria) mRNA biosynthesis (eukaryotes) tRNA and rRNA biosynthesis (bacteria)... 

Fig. 12.4 An Overview of mRNA Biosynthesis Synthesis and Destruction of RNA is used to control metabolism in cells...

The reasons for the decrease of PAL-mRNA biosynthesis in cell cultures of Petroselinum hortense are unknown. Probably product repression is involved. With seedlings of Cucumis sativus in which an increase and subsequent decrease of PAL activity was detected after illumination (as in the cell cultures), it has been shown that... 

Anthranilic acid Actinomycins (D 8.4.1) Inhibitors of transcription of DNA in mRNA biosynthesis, treatment of tumors... 

In addition to codons for ammo acids there are start and stop codons Protein biosynthesis begins at a start codon and ends at a stop codon of mRNA The start codon IS the nucleotide triplet AUG which is also the codon for methionine The stop codons are UAA UAG and UGA... 

Messenger RNA (mRNA) (Section 28 11) A polynucleotide of nbosethat reads the sequence of bases in DNA and inter acts with tRNAs in the nbosomes to promote protein biosynthesis... 

Biosynthesis. The biosynthesis of neuropeptides is much more complex and involves the multistep process of transcription of specific mRNA from specific genes, formation of a high molecular weight protein product by translation, post-translational processing of the protein precursor to allow for... 

Biosynthesis. CRE is derived from a precursor of 196 amino acids (84,85). This gene contains one copy of CRE, which is flanked by double basic amino acids. The amino acid sequence of the CRE precursor suggests that it may arise from proteins related to POMC and neurophysins (31). The CRE precursor contains a cAMP responsive element which aHows stimulation of mRNA synthesis when intraceHular levels of cAMP are increased (86). 

Cellular protein biosynthesis involves the following steps. One strand of double-stranded DNA serves as a template strand for the synthesis of a complementary single-stranded messenger ribonucleic acid (mRNA) in a process called transcription. This mRNA in turn serves as a template to direct the synthesis of the protein in a process called translation. The codons of the mRNA are read sequentially by transfer RNA (tRNA) molecules, which bind specifically to the mRNA via triplets of nucleotides that are complementary to the particular codon, called an anticodon. Protein synthesis occurs on a ribosome, a complex consisting of more than 50 different proteins and several stmctural RNA molecules, which moves along the mRNA and mediates the binding of the tRNA molecules and the formation of the nascent peptide chain. The tRNA molecule carries an activated form of the specific amino acid to the ribosome where it is added to the end of the growing peptide chain. There is at least one tRNA for each amino acid. 

In one of the early experiments designed to elucidate the genetic code, Marshall Nirenberg of the U.S. National Institutes of Health (Nobel Prize in physiology or medicine, 1968) prepared a synthetic mRNA in which all the bases were uracil. He added this poly(U) to a cell-free system containing all the necessary materials for protein biosynthesis. A polymer of a single amino acid was obtained. What amino acid was polymerized ... 

Ribosomal RNAs characteristically contain a number of specially modified nucleotides, including pseudouridine residues, ribothymidylic acid, and methylated bases (Figure 11.26). The central role of ribosomes in the biosynthesis of proteins is treated in detail in Chapter 33. Here we briefly note the significant point that genetic information in the nucleotide sequence of an mRNA is translated into the amino acid sequence of a polypeptide chain by ribosomes. 

The primary cellular function of mRNA is to direct biosynthesis of the thousands of diverse peptides and proteins required by an organism—perhaps 100,000 in a human. The mechanics of protein biosynthesis take place on ribosomes, small granular particles in the cytoplasm of a cell that consist of about 60% ribosomal RNA and 40% protein. 

Figure 28.7 A representation of protein biosynthesis. The codon base sequences on mRNA are read by tRNAs containing complementary anticodon base sequences. Transfer RNAs assemble the proper amino acids into position for incorporation into the growing peptide.

Moore, Stanford, 1030 Morphine, biosynthesis of, 969 specific rotation of, 296 structure of, 64 MR1, see Magnetic resonance imaging. 468-469 mRNA, see Messenger RNA MS, see Mass spectrometry Mullis, Kary Banks, 1117 Multiplct (NMR), 460 table of, 462... 

Not only eukaryotic cells but also bacteria have successfully been targeted by PNA anhsense strategies. Thus it has been shown that PNA complementary to ribosomal RNA or mRNA encoding an essential fatty acid biosynthesis protein, effectively kills E. coli. Furthermore, it has been shown that PNA directed to the start codon of the y -lactamase gene re-sensitized otherwise resistant E. coli to the antibiohc ampiciUin [64—66]. Conjugating a simple transporter peptide to the PNA increased the potency significantly, and an even more potent antibacterial PNA... 

Bannon, M.J. Elliot, PJ. and Bunny, E.B. Striatal tachykinin biosynthesis Regulation of mRNA and peptide levels by dopamine agonists and antagonists. Mol Brain Res 3 31-37, 1987. 

Thompson, A. J., A. C. Jackson et al. (2000a). Abscisic acid biosynthesis in tomato Regulation of zeaxanthin epoxidase and 9-cw-epoxycarotenoid dioxygenase mRNAs by light/dark cycles, water stress and abscisic acid. Plant Mol. Biol. 42(6) 833-845. 

In ah of today s living systems, RNA is involved in processes which are very old from an evolutionary point of view. RNA occurs in protein biosynthesis in three different forms, and thus with three different functions tRNA, mRNA and rRNA. 

A number of stimuli are known to act as inducers of TNF production (Table 9.6). Bacterial LPS represents the most important inducer, and TNF mediates the pathophysiological effects of this molecule. TNF biosynthesis is regulated by both transcriptional and post-transcriptional mechanisms. Macrophages appear to express TNF-a mRNA constitutively, which is translated only... 

The initial hydroxylation of tryptophan, rather than the decarboxylation of 5-HTP, appears to be the rate-limiting step in serotonin synthesis. Therefore, the inhibition of this reaction results in a marked depletion of the content of 5-HT in brain. The enzyme inhibitor most widely used in experiments is parachlorophenylalanine (PCPA). In vivo, PCPA irreversibly inhibits tryptophan hydroxylase, presumably by incorporating itself into the enzyme to produce an inactive protein. This results in a long-lasting reduction of 5-HT levels. Recovery of enzyme activity, and 5-HT biosynthesis, requires the synthesis of new enzyme. Marked increases in mRNA for tryptophan hydroxylase are found in the raphe nuclei 1-3 days after administration of PCPA [6]. 

Whereas DNA is mostly located in the nucleus of cells in higher organisms (with some also in mitochondria and in plant chloroplasts), RNA comes in three major and distinct forms, each of which plays a crucial role in protein biosynthesis in the cytoplasm. These are, respectively, ribosomal RNA (rRNA), which represents two-thirds of the mass of the ribosome, messenger RNA (mRNA), which encodes the information for the sequence of proteins, and transfer RNAs (tRNAs) which serve as adaptor molecules, allowing the 4-letter code of nucleic acids to be translated into the 20-letter code of proteins. These latter molecules contain a substantial number of modified bases, which are introduced enzymatically. 

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