Rocaglates convert DEAD-box protein eIF4A into a sequence-selective translational repressor.
Rocaglamide A (RocA) typifies a class of protein synthesis inhibitors that selectively kill aneuploid tumour cells and repress translation of specific messenger RNAs. RocA targets eukaryotic initiation factor 4A (eIF4A), an ATP-dependent DEAD-box RNA helicase; its messenger RNA selectivity is proposed to reflect highly structured 5' untranslated regions that depend strongly on eIF4A-mediated unwinding. However, rocaglate treatment may not phenocopy the loss of eIF4A activity, as these drugs actually increase the affinity between eIF4A and RNA. Here we show that secondary structure in 5' untranslated regions is only a minor determinant for RocA selectivity and that RocA does not repress translation by reducing eIF4A availability. Rather, in vitro and in cells, RocA specifically clamps eIF4A onto polypurine sequences in an ATP-independent manner. This artificially clamped eIF4A blocks 43S scanning, leading to premature, upstream translation initiation and reducing protein expression from transcripts bearing the RocA-eIF4A target sequence. In elucidating the mechanism of selective translation repression by this lead anti-cancer compound, we provide an example of a drug stabilizing sequence-selective RNA-protein interactions.
Department of Molecular and Cell Biology, Center for RNA Systems Biology, University of California, Berkeley, California 94720, USA.
Shintaro
S
Iwasaki
Department of Molecular and Cell Biology, Center for RNA Systems Biology, University of California, Berkeley, California 94720, USA.
Stephen N
SN
Floor
Department of Molecular and Cell Biology, Center for RNA Systems Biology, University of California, Berkeley, California 94720, USA.
Nicholas T
NT
Ingolia
D020121:5' Untranslated Regions / Q000235:genetics; D000255:Adenosine Triphosphate / Q000378:metabolism; D001572:Benzofurans / Q000494:pharmacology*; D053487:DEAD-box RNA Helicases / Q000737:chemistry / Q000378:metabolism; D039601:Eukaryotic Initiation Factor-4A / Q000737:chemistry / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D006868:Hydrolysis; D009690:Nucleic Acid Conformation; D059372:Nucleotide Motifs; D016366:Open Reading Frames / Q000235:genetics; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects*; D055550:Protein Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity / Q000187:drug effects; D013816:Thermodynamics
D020121:5' Untranslated Regions; D001572:Benzofurans; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C107772:rocaglamide; D000255:Adenosine Triphosphate; D039601:Eukaryotic Initiation Factor-4A; D053487:DEAD-box RNA Helicases