Internal translation initiation mediated by the angiogenic factor Tie2.
Tie2 is an endothelium-specific receptor tyrosine kinase required for normal blood vessel maturation. We report that Tie2 mRNA translation is maintained under hypoxic conditions. To identify the mechanism responsible for this, we undertook structure/function analysis of the Tie2 5'-untranslated region (UTR). Transcription start site mapping indicates the existence of a several mRNA isoforms containing unusually long 5'-UTRs (>350 nucleotides) with five upstream open reading frames. We find internal ribosome binding activity that allows the Tie2 mRNA to initiate in a cap-independent fashion. Our data provide a framework for understanding how Tie2 mRNA is translated despite a cumbersome structured 5'-UTR and how its production is secured under unfavorable environmental conditions.
Park
Eun-Hee
EH
Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada.
Lee
Joseph M
JM
Blais
Jaime D
JD
Bell
John C
JC
Pelletier
Jerry
J
D020121:5' Untranslated Regions; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006801:Humans; D000860:Hypoxia; D008156:Luciferases / Q000378:metabolism; D008715:Methionine / Q000737:chemistry; D008957:Models, Genetic; D008969:Molecular Sequence Data; D018919:Neovascularization, Physiologic; D016366:Open Reading Frames; D010957:Plasmids / Q000378:metabolism; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D020033:Protein Isoforms; D012313:RNA / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D042787:Receptor, TIE-2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases / Q000378:metabolism; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic; D014162:Transfection; D014466:Ultraviolet Rays; D014471:Umbilical Veins / Q000166:cytology / Q000378:metabolism
D020121:5' Untranslated Regions; D017931:DNA Primers; D020033:Protein Isoforms; D012333:RNA, Messenger; D012313:RNA; D004247:DNA; D008715:Methionine; D008156:Luciferases; D042787:Receptor, TIE-2; D012260:Ribonucleases