Transfer RNA Synthesis and Regulation
Published Online: 15 DEC 2009
Copyright © 2001 John Wiley & Sons, Ltd. All rights reserved.
How to Cite
Toh, Y., Hori, H., Tomita, K., Ueda, T. and Watanabe, K. 2009. Transfer RNA Synthesis and Regulation. eLS. .
- Published Online: 15 DEC 2009
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Transfer ribonucleic acid (tRNA) is primarily synthesized from tRNA gene through transcription by RNA polymerase and becomes the mature form via several steps: processing, splicing, CCA addition and posttranscriptional modification. Primary transcripts of tRNA genes contain 5′ and 3′ extra sequences, which are removed by a set of responsible nucleases, and introns in some cases, which are spliced out by a specific endonuclease. The resultant two fragments are joined by RNA ligase. The CCA sequences present at 3′-termini of all mature tRNAs are not encoded in tRNA genes in some species and posttranscriptionally added by a CCA-adding enzyme. All mature tRNA molecules contain modified nucleotides made by modification enzymes and which are considered to be involved in stabilization of tRNA structure, in decoding properties and in correct processing. The concentration of individual tRNA molecules is controlled to maintain cellular functions.
tRNA is synthesized from tRNA gene by RNA polymerase and matured through processing, splicing, CCA addition and posttranscriptional modification.
Synthesis of tRNA is regulated by promoter activity and specific factors (ppGpp and/or pppGpp in prokaryotes and Maf1 in eukaryotes) depending on the nutrient condition of the cells.
The relative amounts of tRNA are regulated by several factors; the copy number of the tRNA gene, transcriptional activity aforementioned and tRNA degradation by a number of nucleases.
Primary transcripts of tRNA genes contain 5′ and 3′ extra sequences, which are removed by a set of responsible nucleases.
In some cases tRNA transcripts contain introns, which are spliced out by a specific endonuclease and the resultant two fragments are joined by RNA ligase.
CCA-adding enzyme regulates the amount of active tRNA by repairing CCA sequence at the C-terminal of tRNA.
tRNA possesses a variety of modified nucleotides which are introduced by modification enzymes during or after the processing, splicing and transport steps.
Several modifications in tRNA play important roles in the translation process, such as enhancement, expansion, restriction and/or alteration of codon–anticodon interactions, stabilization of tRNA structure, recognition by aminoacyl-tRNA synthetase, etc.
- tRNA modification;
- tRNA processing;
- tRNA intron;
- CCA-adding enzyme;
- transcriptional control