Schematic diagram of the genome organization of WU virus, a human polyomavirus with genome structure representative of the family. The "early region" is shown at left and encodes two alternatively spliced proteins, the small and large tumor antigens. The "late region" is shown at right and encodes three viral capsid structural proteins. The regulatory region contains the promoters and transcriptional start sites for both regions, and the origin of replication. The whole genome is 5229 base pairs long and consists of circular double-stranded DNA.