Base-pairing between untranslated regions facilitates translation of uncapped, nonpolyadenylated viral RNA.
Translationally competent mRNAs form a closed loop via interaction of initiation factors with the 5' cap and poly(A) tail. However, many viral mRNAs lack a cap and/or a poly(A) tail. We show that an uncapped, nonpolyadenylated plant viral mRNA forms a closed loop by direct base-pairing (kissing) of a stem loop in the 3' untranslated region (UTR) with a stem loop in the 5' UTR. This allows a sequence in the 3' UTR to confer translation initiation at the 5'-proximal AUG. This base-pairing is also required for replication. Unlike other cap-independent translation mechanisms, the ribosome enters at the 5' end of the mRNA. This remarkably long-distance base-pairing reveals a novel mechanism of cap-independent translation and means by which mRNA UTRs can communicate.
Guo
L
L
Interdepartmental Genetics, Plant Pathology Department, 351 Bessey Hall, Iowa State University, Ames, IA 50011, USA.
Allen
E M
EM
Miller
W A
WA
D020413:3' Untranslated Regions / Q000378:metabolism*; D020121:5' Untranslated Regions / Q000378:metabolism*; D000595:Amino Acid Sequence; D020029:Base Pairing; D017124:Conserved Sequence; D017793:Luteovirus / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D011061:Poly A / Q000235:genetics*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D016415:Sequence Alignment
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D012333:RNA, Messenger; D012367:RNA, Viral; D011061:Poly A