The 5'-poly(A) leader of poxvirus mRNA confers a translational advantage that can be achieved in cells with impaired cap-dependent translation

• Published in: PLoS pathogens 2017-08, Vol.13 (8), p.e1006602-e1006602
• Main Authors: Dhungel, Pragyesh, Cao, Shuai, Yang, Zhilong
• Format: Article
• Language: English
• Subjects: 5' Untranslated Regions; 5' Untranslated Regions - genetics; Biology; Biology and life sciences; Blotting, Western; Cell cycle; Cell Line; Cytomegalovirus; Deoxyribonucleic acid; DNA; DNA biosynthesis; DNA replication; Gene expression; Gene Knockdown Techniques; Genetic aspects; Guanosine; Health aspects; Humans; Infections; Internal ribosome entry site; Kinases; Leadership; Messenger RNA; mRNA; Physiological aspects; Poly(A); Polymerase Chain Reaction; Poxviridae Infections - genetics; Poxviruses; Protein Biosynthesis - genetics; Protein sorting signals; Protein synthesis; Proteins; Research and analysis methods; Residues; RNA Caps - genetics; RNA polymerase; RNA, Messenger - genetics; RNA, Viral - genetics; Translation; Translation (Genetics); Vaccinia virus - genetics; Viral infections; Virus Replication - genetics; Viruses
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1006602

The poly(A) leader at the 5'-untranslated region (5'-UTR) is an unusually striking feature of all poxvirus mRNAs transcribed after viral DNA replication (post-replicative mRNAs). These poly(A) leaders are non-templated and of heterogeneous lengths; and their function during poxvirus infection remains a long-standing question. Here, we discovered that a 5'-poly(A) leader conferred a selective translational advantage to mRNA in poxvirus-infected cells. A constitutive and uninterrupted 5'-poly(A) leader with 12 residues was optimal. Because the most frequent lengths of the 5'-poly(A) leaders are 8-12 residues, the result suggests that the poly(A) leader has been evolutionarily optimized to boost poxvirus protein production. A 5'-poly(A) leader also could increase protein production in the bacteriophage T7 promoter-based expression system of vaccinia virus, the prototypic member of poxviruses. Interestingly, although vaccinia virus post-replicative mRNAs do have 5'- methylated guanosine caps and can use cap-dependent translation, in vaccinia virus-infected cells, mRNA with a 5'-poly(A) leader could also be efficiently translated in cells with impaired cap-dependent translation. However, the translation was not mediated through an internal ribosome entry site (IRES). These results point to a fundamental mechanism poxvirus uses to efficiently translate its post-replicative mRNAs.