PolyomavirusPolyomavirus InfectionsAntigens, Polyomavirus TransformingMerkel cell polyomavirusCarcinoma, Merkel CellBK VirusJC VirusAntigens, Viral, TumorDNA, ViralTumor Virus InfectionsDNA ReplicationSimian virus 40Virus ReplicationEnhancer Elements, GeneticCell Transformation, ViralBase SequenceMerkel CellsGenes, ViralCell LineRecombination, GeneticMolecular Sequence DataCapsid ProteinsTranscription, GeneticLeukoencephalopathy, Progressive MultifocalPolyomaviridaeCapsidUrineProto-Oncogene Proteins pp60(c-src)3T3 CellsGenome, ViralOncogene Proteins, ViralViral Regulatory and Accessory ProteinsGene Expression Regulation, Viral