Looking at the DNA (or RNA?) sequence of the Covid-19 virus here: https://www.ncbi.nlm.nih.gov/nuccore/MN908947.3

I notice it ends in 33 a's. Does the virus really look like that, or is it some artifact of the sequencing process, or some sort of padding to round out numbers?

Here's the last few lines:

29761 acagtgaaca atgctaggga gagctgccta tatggaagag ccctaatgtg taaaattaat
29821 tttagtagtg ctatccccat gtgattttaa tagcttctta ggagaatgac aaaaaaaaaa
29881 aaaaaaaaaa aaaaaaaaaa aaa

1 Answer 1


This is a poly(A) tail, which is a feature found in the majority of eukaryotic RNAs (especially mRNA) and is also not uncommon in RNA viruses (which essentially mimic endogenous mRNA for their own replication). As with mRNA, this poly(A) tail in coronaviruses is bound by poly(A) binding protein in the cytoplasm [1], which is involved in translation initiation. In coronaviruses, this poly(A) tail is also necessary for replication independent of its role in translation [2].

[1] Lin Y-J, Liao C-L, Lai MM. 1994. Identification of the cis-acting signal for minus-strand RNA synthesis of a murine coronavirus: implications for the role of minus-strand RNA in RNA replication and transcription. J Virol 68(12):8131-8140.

[2] Spagnolo JF, Hogue BG. 2000. Host protein interactions with the 3′ end of bovine coronavirus RNA and the requirement of the poly (A) tail for coronavirus defective genome replication. J Virol 74(11):5053-5065.


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