Large T and small T antigens of Merkel cell polyomavirus

- Merkel cell polyomavirus (MCV) is a newly discovered human tumor virus that causes Merkel cell carcinoma (MCC).
- MCV is clonally integrated in MCC tumor cells.
- Large T antigens carry signature C-terminal truncations in MCC.
- MCV-associated tumorigenesis is characterized by the expression of LT and sT antigens.
- Functional domains and motifs of LT and sT mediate MCV tumorigenesis.

Merkel cell polyomavirus (MCV) is the etiological agent of Merkel cell carcinoma (MCC), a rare and highly lethal human skin cancer. A natural component of skin flora, MCV becomes tumorigenic only after integration into the host DNA together with specific mutations to the viral genome. Research on MCV large T (LT) and small T (sT) antigens, the only viral products expressed in MCC, shows that these major oncoproteins not only possess biochemical functions found in common with other polyomavirus T antigens, but also demonstrate new cellular targets not described in previous polyomavirus models. This review provides a map of the relevant functional motifs and domains in MCV T antigens that have been identified, highlighting their roles in tumorigenesis.