Evolutionary relationships of the hexon and penton base genes of novel squirrel adenovirus

Squirrel adenovirus (SqAdV) was reported previously. However, only partial sequences of its hexon and polymerase genes have been revealed. For the first time, we report the full-length genome of SqAdV including the complete hexon and penton base genes. From internal body organs of 59 red squirrels archived in Korea Bank for Pathogenic Viruses, the hexon, penton base, and full-length genome of SqAdV were determined by a PCR method. Of the internal body organs examined, the spleen showed the highest detection rate (25.42%) for SqAdV whereas the kidney and lung exhibited 18.64% and 3.39% rates, respectively. Based on the phylogenetic relationships of the hexon and penton base genes, SqAdV appears to belong to the genus Mastadenovirus, and, at least in our study, the hexon of SqAdV exhibits the closest relationship to that of an alpaca AdV. Compared with the hexon, the penton base of SqAdV appears to be genetically more divergent from that of other mastadenoviruses. It was also revealed that the full-length SqAdV genome retained AT nucleotide content similar level to AT-rich atadenoviruses, which is unusual for mastadenoviruses. Our results emphasize that SqAdV is classified into the genus Mastadenovirus and demonstrate the AT-biased nucleotide constitution of SqAdV.