ABSTRACT
The non-coding control region (NCCR) of polyomaviruses includes the promoters for early and late genes, a transcription enhancer and the origin of DNA replication. Particularly virulent variants of the human pathogens BKPyV and JCPyV, as well as of simian virus 40 (SV40), occur in vitro and in vivo. These strains often harbour rearrangements in their NCCR, typically deletions of some DNA segment(s) and/or duplications of others. Using an SV40-based model system we provide evidence that duplications of enhancer elements, whether from SV40 itself or from the related BKPyV and JCPyV, increase early gene transcription and replicative capacity. SV40 harbouring subsegments of the strong cytomegalovirus (HCMV) enhancer replicated better than the common 'wild-type' SV40 in the human cell lines HEK293 and U2OS. In conclusion, replacing the SV40 enhancer with heterologous enhancers can profoundly influence SV40's infective capacity, underscoring the potential of small DNA viruses to overcome cell type and species barriers.
Subject(s)
BK Virus/genetics , DNA, Viral/genetics , Enhancer Elements, Genetic/genetics , JC Virus/genetics , Simian virus 40/genetics , Viral Tropism/genetics , Animals , BK Virus/growth & development , BK Virus/physiology , Base Sequence , Cell Line , Chlorocebus aethiops , Cytomegalovirus/genetics , DNA Replication/genetics , HEK293 Cells , Hep G2 Cells , Humans , JC Virus/growth & development , JC Virus/physiology , Mice , Promoter Regions, Genetic/genetics , Simian virus 40/growth & development , Simian virus 40/physiology , Transcription, Genetic/genetics , Viral Tropism/physiologyABSTRACT
In simian virus 40 (SV40) and several other polyomaviruses, the TATA box of the early promoter is embedded in an AT tract that is also an essential part of the replication origin. We generated an 'AT trap', an SV40 genome lacking the AT tract and unable to grow in CV-1 monkey cells. Co-transfection of the AT trap with oligonucleotides containing AT tracts of human polyomaviruses, a poly(A : T) tract or variants of the SV40 WT sequence all restored infectious virus. In a transfection of the AT trap without a suitable oligonucleotide, an AT-rich segment was incorporated, stemming either from bovine (calf serum) or monkey (host cell) DNA. Similarly, when cells were grown with human serum, a human DNA segment was captured by SV40 to substitute for the missing AT stretch. We conclude that the virus is quite opportunistic in accepting heterologous substitutes, and that even low-abundance DNA from serum can be incorporated into the viral genome.
