ZC3HAV1 and influenza: To investigate whether differences in ZAP function in ducks, chickens and mammalian cells led to systematic differences of CpG and UpA representation, we analyzed dinucleotide compositions in a large data set of representative isolates of IAV with annotated hosts from the Influenza Research Database (mammalian: 2949 isolates, primarily H1N1 and H3N2 serotypes; avian: 6417 isolates; Supplemental Data Tables S14, S15).