Temporal translational control by a metastable RNA structure.
Programmed cell death by the hok/sok locus of plasmid R1 relies on a complex translational control mechanism. The highly stable hok mRNA is activated by 3'-end exonucleolytical processing. Removal of the mRNA 3' end releases a 5'-end sequence that triggers refolding of the mRNA. The refolded hok mRNA is translatable but can also bind the inhibitory Sok antisense RNA. Binding of Sok RNA leads to irreversible mRNA inactivation by an RNase III-dependent mechanism. A coherent model predicts that during transcription hok mRNA must be refractory to translation and antisense RNA binding. Here we provide genetic evidence for the existence of a 5' metastable structure in hok mRNA that locks the nascent transcript in an inactive configuration in vivo. Consistently, the metastable structure reduces the rate of Sok RNA binding and completely blocks hok translation in vitro. Structural analyses of native RNAs strongly support that the 5' metastable structure exists in the nascent transcript. Further structural analyses reveal that the mRNA 3' end triggers refolding of the mRNA 5' end into the more stable tac-stem conformation. These results provide a profound understanding of an unusual and intricate post-transcriptional control mechanism.
Møller-Jensen
J
J
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense University, DK-5230 Odense M, Denmark.
Franch
T
T
Gerdes
K
K
D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins; D001483:Base Sequence; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012313:RNA; D012329:RNA, Bacterial; D012333:RNA, Messenger / Q000737:chemistry / Q000502:physiology*
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; C087026:Sok antisense RNA, E coli; D012313:RNA