Presence Of Poly(A) And Poly(A)-rich Tails In A Positive-strand RNA Virus Known To Lack 3' Poly(A) Tails

In this study, we show that Tobacco mosaic virus (TMV), a positive-strand RNA virus known to end with 3'tRNA-like structures, does possess a small fraction of gRNA bearing polyadenylate tails. Particularly, many tails are at sites corresponding to the 3'end of near full length gRNA, and are composed of poly(A)-rich sequences containing the other nucleotides in addition to adenosine, resembling the degradation-stimulating poly(A) tails observed in all biological kingdoms. Further investigations demonstrate that these polyadenylated RNA species are not enriched in chloroplasts. Silencing of cpPNPase, a chloroplast-localized polynucleotide polymerase known to not only polymerize the poly(A)-rich tails but act as a 3' to 5' exoribonuclease, doesn't change the profile of polyadenylate tails associated with TMV RNA. Nevertheless, because similar tails were also detected in other phylogenetically distinct positive-strand RNA viruses lacking poly(A) tails, such kind of polyadenylation may reflect a common but as-yet-unknown interface between hosts and viruses.