Polyadenylation is dispensable for encapsidation and reverse transcription of hepatitis B viral pregenomic RNA

A hepadnaviruses replicates its DNA genome via reverse transcription of an RNA template (pregenomic RNA or pgRNA), which has a cap structure at the 5' end and a poly(A) tail at the 3' end. We have previously shown that the 5' cap is indispensable for encapsidation of the pgRNA. A speculative extension of the above finding is that the cap contributes to encapsidation via its interaction with the poly(A) tail, possibly involving eIF4E-eIF4G-PABP interaction. To test this hypothesis, poly(A)-less pgRNAs were generated via cleavage by a cis-acting hepatitis delta virus ribozyme sequence. We found that accumulation of the poly(A)less pgRNA was markedly diminished, mostly likely due to its reduced stability. Importantly, however, the remaining poly(A)-less pgRNAs were nonetheless encapsidated and reverse transcribed normally when the reduced stability was taken account. Our finding clearly contradicts the notion that the poly(A) tail has any function in encapsidation and viral reverse transcription.