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Updated: Jun 20, 2026
Merkel Cell Polyomavirus Infection and Detection
Published on: February 7, 2019
The minimum replication origin of merkel cell polyomavirus has a unique large T-antigen loading architecture and
Hyun Jin Kwun1, Anna Guastafierro, Masahiro Shuda
1Molecular Virology Program, University of Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
Abstract:
Merkel cell polyomavirus (MCV) is a recently discovered human polyomavirus causing the majority of human Merkel cell carcinomas. We mapped a 71-bp minimal MCV replication core origin sufficient for initiating eukaryotic DNA replication in the presence of wild-type MCV large T protein (LT). The origin includes a poly(T)-rich tract and eight variably oriented, GAGGC-like pentanucleotide sequences (PS) that serve as LT recognition sites. Mutation analysis shows that only four of the eight PS are required for origin replication. A single point mutation in one origin PS from a naturally occurring, tumor-derived virus reduces LT assembly on the origin and eliminates viral DNA replication. Tumor-derived LT having mutations truncating either the origin-binding domain or the helicase domain also prevent LT-origin assembly. Optimal MCV replication requires coexpression of MCV small T protein (sT), together with LT. An intact DnaJ domain on the LT is required for replication but is dispensable on the sT. In contrast, PP2A targeting by sT is required for enhanced replication. The MCV origin provides a novel model for eukaryotic replication from a defined DNA element and illustrates the selective pressure within tumors to abrogate independent MCV replication.
Insights
Merkel cell polyomavirus (MCV) replication requires a specific origin sequence and large T protein (LT). Tumor mutations disrupt this origin, preventing viral DNA replication and highlighting cancer-driven evolutionary pressures.
Area of Science:
- Virology
- Molecular Biology
- Oncology
Background:
- Merkel cell polyomavirus (MCV) is a human polyomavirus linked to Merkel cell carcinoma.
- Understanding MCV replication is crucial for comprehending viral oncogenesis.
Purpose of the Study:
- To identify and characterize the minimal replication core origin of MCV.
- To investigate the role of MCV large T (LT) and small T (sT) proteins in viral DNA replication.
- To explore how tumor-derived mutations affect MCV replication.
Main Methods:
- DNA replication assays using a defined 71-bp MCV minimal origin.
- Site-directed mutagenesis of the origin and LT/sT proteins.
- Analysis of LT binding to the origin.
- Assessing the impact of tumor-derived mutations.
Main Results:
- A 71-bp minimal MCV replication origin was mapped, containing a poly(T)-rich tract and eight GAGGC-like pentanucleotide sequences (PS).
- Only four of the eight PS are essential for replication; mutations in these sites abolish replication.
- Tumor-derived mutations in the origin or LT protein prevent LT assembly and viral DNA replication.
- Optimal replication requires co-expression of LT and sT, with specific domains playing critical roles.
Conclusions:
- The MCV origin serves as a novel model for eukaryotic DNA replication initiation.
- Tumorigenesis involves selective pressures that abrogate independent MCV replication.
- MCV LT and sT proteins, along with the viral origin, are key determinants of viral replication.
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