Giant viruses from the Mimiviridae family replicate entirely in their host cytoplasm where their genes are transcribed by a viral transcription apparatus. mRNA polyadenylation uniquely occurs at hairpin-forming palindromic sequences terminating viral transcripts. Here we show that a conserved gene cluster both en-code the enzyme responsible for the hairpin cleavage and the viral polyA polymerases (vPAP). Unexpect-edly, the vPAPs are homodimeric and uniquely self-processive. The vPAP backbone structures exhibit a symmetrical architecture with two subdomains shar-ing a nucleotidyltransferase topology, suggesting that vPAPs originate from an ancestral duplication. A Poxvirus processivity factor homologue encoded by Megavirus chilensis displays a conserved 5′-GpppA 2′O methyltransferase activity but is also able to in-ternally methylate the mRNAs ’ polyA tails. These findings elucidate how the arm wrestling between hosts and their viruses to access the translation ma-chinery is taking place in Mimiviridae
To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.