Hamster polyomavirus (HaPV) is a small, circular DNA virus which belongs to the papovavirus family. HaPV was originally isolated from skin epitheliomas originating from hair follicle epithelial cells in Syrian golden hamsters. High levels of virus DNA replication and progeny virion production has been detected in epitheliomas of infected hamsters. In some infected animals, HaPV can also cause lymphomas. The viral genome is defective in lymphoid tumors and although there is a high level of DNA replication, no progeny virion are produced. The genome of HaPV has three distinct regions: the early protein coding region which codes for three proteins expressed directly after infection; the late protein coding region which codes for the three viral structural proteins; the noncoding region which contains all of the sequences which control transcription of both the early and late region messenger RNAs and sequences which affect viral DNA replication. Studies have been continued to elucidate the important biological roles for each of these regions in virus replication and cellular transformation.
