The CCA-adding enzyme, which builds and repairs the 3′ terminal CCA sequence of tRNA, is the only RNA polymerase that can synthesize a defined nucleotide sequence without using a nucleic acid template. New cocrystal structures tell us how this remarkable enzyme works.
Weiner, A. M. (2004, October 26). tRNA maturation: RNA polymerization without a nucleic acid template. Current Biology. Cell Press. https://doi.org/10.1016/j.cub.2004.09.069