tRNA transfers to the limelight
- Anita K. Hopper1,3 and
- Eric M. Phizicky2
- 1Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA; 2Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, New York 14642, USA
This extract was created in the absence of an abstract.
tRNA has a central role in biology as the adaptor between mRNA and protein, in which anticodon interactions with the mRNA codon at one end of the L-shaped tRNA allow an attached amino acid at the other end of the tRNA to condense with the peptide chain on a second tRNA through the action of the ribosome. This familiar role of tRNA requires mature tRNAs to be recognized by the aminoacyl tRNA synthetase to add the amino acid to its 3′ end, by EF1α to form a ternary complex with the aminoacylated tRNA and GTP, and by elements of the ribosome and associated components to allow binding, peptide synthesis, and translocation. Before fulfilling this role, all tRNA transcripts have to be extensively processed. Maturation of tRNAs requires five major steps: (1) removal of the 5′ leader by RNase P, which almost universally requires a ribonucleoprotein complex; (2) removal of the 3′ trailer sequence by some combination of endonucleases and exonucleases; (3) addition of CCA in eukaryotes, many eubacteria, and some archaea; (4) splicing of introns in some tRNAs of most (if not all) eukaryotes and some archaea, by an endonuclease that excises the intron and a ligase that joins the exons; and (5) numerous modifications of tRNA at multiple residues (see Fig.1).
A schematic of a tRNA precursor and a mature tRNA. Each nucleotide is represented by a filled circle: part of the mature tRNA (green); leader and trailer sequences (purple); intron (blue); anticodon (red). The positions of several of the tRNA modifications discussed in the text are indicated on the canonical tRNA molecule shown at the right, using the usual tRNA numbering system. For reviews of the modifications, see Björk (1995) and Sprinzl et al. (1998).
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