Structures required for poly(A) tail-independent translation overlap with, but are distinct from, cap-independent translation and RNA replication signals at the 3' end of Tobacco necrosis virus RNA.
Tobacco necrosis necrovirus (TNV) RNA lacks both a 5' cap and a poly(A) tail but is translated efficiently, owing in part to a Barley yellow dwarf virus (BYDV)-like cap-independent translation element (BTE) in its 3' untranslated region (UTR). Here, we identify sequence downstream of the BTE that is necessary for poly(A) tail-independent translation in vivo by using RNA encoding a luciferase reporter gene flanked by viral UTRs. Deletions and point mutations caused loss of translation that was restored by adding a poly(A) tail, and not by adding a 5' cap. The two 3'-proximal stem-loops in the viral genome contribute to poly(A) tail-independent translation, as well as RNA replication. For all necroviruses, we predict a conserved 3' UTR secondary structure that includes the BTE at one end of a long helical axis and the stem-loops required for poly(A) tail-independent translation and RNA replication at the other end. This work shows that a viral genome can harbor distinct cap- and poly(A) tail-mimic sequences in the 3' UTR.
Shen
Ruizhong
R
Interdepartmental Genetics Program and Department of Plant Pathology, Iowa State University, IA 50011, USA.
Miller
W Allen
WA
D020413:3' Untranslated Regions / Q000737:chemistry / Q000502:physiology*; D018554:Avena; D001483:Base Sequence; D016679:Genome, Viral; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D011523:Protoplasts; D012367:RNA, Viral / Q000096:biosynthesis*; D019183:Tombusviridae / Q000235:genetics*
D020413:3' Untranslated Regions; D012367:RNA, Viral