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. Author manuscript; available in PMC: 2014 Feb 19.
Published in final edited form as: Nat Rev Microbiol. 2013 Mar 11;11(4):264–276. doi: 10.1038/nrmicro2992

Figure 1. Genomic organization and structure of polyomaviruses.

Figure 1

a | The prototypical circular double-stranded DNA genome has three main regions: a non-coding control region containing the early and late promoters, their transcription start sites and the origin of replication; an early region encoding large T antigen (LT) and small T antigen (ST) and an alternatively spliced LT (LT′); and a late region encoding the viral coat proteins VP1, VP2, VP3 and VP4. The reading frames for VP2, VP3 and VP4 are identical, but translation starts at successive initiating AUG codons to generate the different proteins. VP4 has been confirmed only in the primate species simian virus 40 (SV40). Agnoprotein (Agno) is encoded by a late transcript from JC polyomavirus and BK polyomavirus, but has yet to be confirmed in the new human polyomaviruses. b | Electron micrograph of purified recombinant VP1 pentamers (from murine polyomavirus), which have a diameter of ~9 nm (scale bar represents 100 nm). c | Electron micrograph of purified murine polyomavirus virions, which have a diameter of ~50 nm (scale bar represents 200 nm).