RNase T2 Family: Enzymatic Properties, Functional Diversity, and Evolution of Ancient Ribonucleases

Abstract

RNase T2 enzymes are transferase-type endoribonucleases that produce oligonucleotides and/or mononucleotides with a terminal 3 0 phosphate via a 2 0 ,3 0 cyclic phosphate intermediate. These RNases are found in all eukaryotes and also in bacteria and viruses, where they have a wide range of biological activities. Some have a housekeeping role, degrading rRNA, and mutations affecting this function result in alterations in cellular homeostasis and are associated with brain lesions in vertebrates. Others have a variety of specialized roles including antimicrobial defense, phosphate scavenging, rejection of “self” pollen, and even nitrogen storage. Members of this family have also acquired functions that are independent of their ribonuclease activity. One of these catalysis-independent functions is implicated in the control of cellular growth, and lack of RNASET2 protein in humans is correlated with several classes of tumors. This review will discuss the basic structure, enzy- matic properties, and biological roles of this ancient RNase family.