Guanine-N7 methyltransferase (NSP14) possessing two different activities: an exoribonuclease activity acting on both ssRNA and dsRNA in a 3' to 5' direction and a N7-guanine methyltransferase activity. The nsp10/nsp14 complex hydrolyzes double-stranded RNA in a 3' to 5' direction as well as a single mismatched nucleotide at the 3'-end mimicking an erroneous replication product. In contrast, di-, tri-, and longer unpaired ribonucleotide stretches, as well as 3'-modified RNAs, resist nsp10/nsp14-mediated excision. Nsp10 forms a dodecamer and interacts with nsp14 and nsp16; these interactions enhance nsp14 and nsp16 enzymatic activities. Nsp14 interacts (via N-terminus) with DDX1.