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About 40 years ago, the large and small tumor antigens (LT-Ag and sT-Ag) of the polyomavirus (PyVs) simian vacuolating virus 40 have been identified and characterized. To date, it is well known that all the discovered human PyVs (HPyVs) encode these 2 multifunctional and tumorigenic proteins, expressed at viral replication early stage. The 2 T-Ags are able to transform cells both in vitro and in vivo and seem to play a distinct role in the pathogenesis of some tumors in humans. In addition, they are involved in viral DNA replication, transcription, and virion assembly. This short review focuses on the structural and functional features of the HPyVs' LT-Ag and sT-Ag, with special attention to their transforming properties., Competing Interests: Declaration of conflicting interests:The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Merkel cell polyomavirus (MCPyV) large T antigen (LT-ag) is frequently found truncated in Merkel cell carcinomas (MCC) and it is considered a major tumor-specific signature. Nonetheless, the biological role of LT-ag nontruncated mutations is largely unknown. In this study, MCPyV LT-ag second exon from 11 non-MCC oral samples and NCBI sequences derived from different anatomical sites were studied from the genetic and structural standpoint. As expected, the LT-ag mutation profile was influenced by the geographical origin of the sample, although nonsynonymous mutations were more frequent in lesional tissues. Our in silico study suggests that the mutations found would not significantly affect protein functions, regardless of sample category. This work presents a thorough investigation of the structural and functional properties of LT-ag nontruncated mutations in MCPyV. Our results sustain the geographical influence of the MCPyV genetic profile, but do not discard genetic tissue specificities. Further investigation involving other genetic segments in healthy and lesional tissues are necessary to improve our knowledge on MCPyV pathogenesis., (© 2014 S. Karger AG, Basel.)