RNA polymerase III also transcribes tRNA genes from internal promoters, but unlike the 5S rRNA genes, tRNA genes tend to cluster in the genome (below).
tRNA primary transcripts are processed by
- enzymatic addition of -C-C-A base triplet at the 3' end
- the modification of bases internal to the molecule
A yeast tRNA showing these modifications is illustrated below.
The tRNA folds into several hairpin loops based on internal H-bond formation between complementary bases in the molecule. The 3’-terminal A residue of this (and every) tRNA will bind to an amino acid specific for the tRNA.
200 tRNA Transcription and Processing