Transfer RNA (tRNA)

Genes coding for tRNAs are clustered in both prokaryotes and eukaryotes. Some of the tRNA genes are located within the spacer regions of the ribosomal gene clusters.

The majority of tRNA genes is clustered as a group in the DNA, and frequently occurs in –two to three copies. In Drosophila, 284 tRNA genes have been identified. In humans there are 497 (plus 324 pseudogenes), in Caenorhabditis 584 tRNA genes. Some E. coli tRNA (86) gene clusters include genes for proteins. The tRNA genes within the cluster are separated by intergenic sequences and are transcribed as long pre-tRNA sequences. The primary transcript is processed at the 5′-end by RNase P and at the 3′-end by RNase D, BN, T, PH, RNase II, and polynucleotide phosphorylase. The pre-tRNA processing also involves joining the fragments after introns are removed by tRNA ligase multifunctional enzymes (Englert M, Beier H 2005 Nucleic Acids Res 33:388). In the Nanoarchaeum equitansbacterium, separate sequences code for the 5′ and 3′...