Abstract
Oligoribonuclease (Orn) is an essential ribonuclease (RNase) from Escherichia coli (E. coli), which plays a critical role in the conversion of short RNA molecules (NanoRNAs) to mononucleotides. Although no additional functions have been ascribed to Orn since its discovery nearly 50 years ago, it was observed in this study that the growth defects caused by a lack of two other RNases that do not digest NanoRNAs, polynucleotide phosphorylase, and RNase PH, could be suppressed by overexpression of Orn. Further analyses showed that overexpression of Orn can alleviate the growth defects caused by an absence of other RNases even when its expression was increased by a small degree, and it can carry out molecular reactions that are normally performed by RNase T and RNase PH. In addition, biochemical assays revealed that Orn can fully digest single-stranded RNAs within a variety of structural contexts. These studies provide new insights into Orn function and its ability to participate in multiple aspects of E. coli RNA metabolism.