Translation of an uncapped mRNA involves scanning

Gunnery, S., Maivali, U., Mathews, M. B. (August 1997) Translation of an uncapped mRNA involves scanning. Journal of Biological Chemistry, 272 (34). pp. 21642-6. ISSN 0021-9258 (Print)



tat, an essential gene of human immunodeficiency virus, when placed under the control of the RNA polymerase III promoter from the adenovirus VA RNA1 gene, is transcribed into an uncapped and nonpolyadenylated mRNA. This VA-Tat RNA is translated to produce functional Tat protein in transfected mammalian cells (Gunnery, S., and Mathews, M. B. (1995) Mol. Cell. Biol. 15, 3597-3607). The presence of an upstream open reading frame (ORF) in VA-Tat RNA is inhibitory to the translation of the Tat ORF, suggesting that the RNA is scanned during translation even though it is uncapped. Because the effect of the upstream ORF is relatively small (about 2-fold), we sought more definitive evidence of scanning by introducing secondary structures of varying stabilities into the 5'-untranslated region of VA-Tat RNA. The results of transfection experiments showed that highly stable secondary structure was inhibitory to Tat synthesis, whereas structures of lower stability were not inhibitory, confirming that uncapped mRNA is subject to scanning. Furthermore, translation of the downstream ORF was reduced but not eliminated by mutations that caused the upstream ORF to overlap the Tat ORF. Extending the overlap of the two ORFs further decreased the translation of the downstream ORF. This observation implies that ribosomes reinitiate after termination, possibly after migrating in a 3' to 5' direction through the overlap region of the mRNA. Similar results were obtained with a capped polymerase II transcript, indicating that the translation of polymerase II and polymerase III transcripts occurs through similar mechanisms.

Item Type: Paper
Uncontrolled Keywords: Genes, tat Hela Cells Humans Nucleic Acid Conformation Peptide Chain Initiation, Translational Promoter Regions (Genetics) RNA Caps RNA Polymerase II/metabolism RNA Polymerase III/metabolism RNA, Messenger/ genetics/ultrastructure RNA, Viral/ genetics Research Support, U.S. Gov't, P.H.S.
Subjects: bioinformatics > genomics and proteomics > design > protein network design > peptide design
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > enzymes > RNA polymerase
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > genes, structure and function > genes: types
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > mRNA
CSHL Authors:
Communities: CSHL labs
Depositing User: Kathleen Darby
Date: 22 August 1997
Date Deposited: 07 May 2014 18:06
Last Modified: 07 May 2014 18:06
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