RNA 3’-terminal phosphate cyclases and cyclase-like proteins

Abstract

RNA molecules bearing terminal 2’,3’-cyclic phosphate are quite common in nature. For example, 2’,3’-cyclic phosphate termini are produced during RNA cleavage by many en-doribonucleases either as intermediates or final products. Many RNA-based nucleases (ribo-zymes) also generate cyclic phosphate termini. However, cleavage reactions are not the only way in which RNAs bearing cyclic phosphate ends are produced. They can also be generated by RNA 3’-terminal phosphate cyclases (RtcA), a family of enzymes conserved in eukaryotes, bacteria, and archaea. These enzymes catalyze the ATP-dependent conversion of the 3’-phos-phate to a 2’,3’-cyclic phosphodiester at the end of RNA. In this article, I review knowledge about the biochemistry and structure of RNA 3’-phosphate cyclases and also proteins of the RNA cyclase-like (Rcl1) family, and discuss their documented or possible roles in different RNA metabolic reactions.