Replication-coupled maturation of readthrough late transcripts by a polyomavirus small T antigen

In Merkel cell polyomavirus (MCV), small T antigen (sT) restores replication-coupled maturation of late wraparound transcripts, enabling splicing and VP1/VP2 mRNA production.

• Why it matters: Late gene expression depends on converting non-polyadenylated readthrough RNAs into properly processed cytoplasmic mRNAs, but how sT coordinates this maturation was unclear.
• What they did: Using MCV{Delta}sT, RNA sequencing and a dual-fluorescence reporter, the authors showed that exogenous sT—sensitive to aphidicolin and requiring replication-activating chromatin-binding domains—promotes splicing and polyadenylation of wraparound transcripts.
• The result: sT increased cytoplasmic VP1 and VP2 mRNA levels and improved use of the leaky late poly(A) signal, while co-expression with LT abolished the effect, and sT from HPyV7 and HPyV9 similarly rescued the defect.

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