Short RNAs repress translation after initiation in mammalian cells.
MicroRNAs (miRNAs) are predicted to regulate 30% of mammalian protein-encoding genes by interactions with their 3' untranslated regions (UTRs). We use partially complementary siRNAs to investigate the mechanism by which miRNAs mediate translational repression in human cells. Repressed mRNAs are associated with polyribosomes that are engaged in translation elongation, as shown by puromycin sensitivity. The inhibition appears to be postinitiation because translation driven by the cap-independent processes of HCV IRES and CrPV IRES is repressed by short RNAs. Further, metabolic labeling suggests that silencing occurs before completion of the nascent polypeptide chain. In addition, silencing by short RNAs causes a decrease in translational readthrough at a stop codon, and ribosomes on repressed mRNAs dissociate more rapidly after a block of initiation of translation than those on control mRNAs. These results suggest that repression by short RNAs, and thus probably miRNAs, is primarily due to ribosome drop off during elongation of translation.
Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Christian P
CP
Petersen
Marie-Eve
ME
Bordeleau
Jerry
J
Pelletier
Phillip A
PA
Sharp
D000818:Animals; D002460:Cell Line; D018388:Codon, Terminator; D005786:Gene Expression Regulation; D020868:Gene Silencing; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D010443:Peptide Chain Termination, Translational; D010455:Peptides / Q000378:metabolism; D010458:Peptidyl Transferases / Q000378:metabolism; D014176:Protein Biosynthesis; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism
D018388:Codon, Terminator; D035683:MicroRNAs; D010455:Peptides; D034741:RNA, Small Interfering; D010458:Peptidyl Transferases