Besides RNA-dependent RNA polymerase, RNA helicase, and protease activities, which are common to RNA viruses, the coronavirus replicase was recently predicted to employ a variety of RNA processing enzymes that are not (or extremely rarely) found in other RNA viruses and include putative sequence-specific endoribonuclease, 3′-to-5′ exoribonuclease, 2′ - O - ribose methyltransferase, ADP ribose 1′-phosphatase and, in a subset of group 2 coronaviruses, cyclic phosphodiesterase activities.