COPA and hepatocellular carcinoma: In the nucleus, ADAR1p110 edits A-C mismatched base pairs of telomeric RNA: DNA hybrids, which facilitates RNase H2 processing of the telomere R-loop and promotes genomic stability.239 ADAR2 has a similar effect.240 Song et al.241 reported that ADAR2-mediated editing of COPA pre-mRNA results in an isoleucine-to-valine substitution at residue 164 in hepatocellular carcinoma, which produces a less stable protein and switches COPA from an oncogenic gene to a suppressor by deactivating PI3K/AKT/mTOR signaling.