Ribosomal protein S15 represses its own translation via adaptation of an rRNA-like fold within its mRNA.
The 16S rRNA-binding ribosomal protein S15 is a key component in the assembly of the small ribosomal subunit in bacteria. We have shown that S15 from the extreme thermophile Thermus thermophilus represses the translation of its own mRNA in vitro, by interacting with the leader segment of its mRNA. The S15 mRNA-binding site was characterized by footprinting experiments, deletion analysis and site-directed mutagenesis. S15 binding triggers a conformational rearrangement of its mRNA into a fold that mimics the conserved three-way junction of the S15 rRNA-binding site. This conformational change masks the ribosome entry site, as demonstrated by direct competition between the ribosomal subunit and S15 for mRNA binding. A comparison of the T.thermophilus and Escherichia coli regulation systems reveals that the two regulatory mRNA targets do not share any similarity and that the mechanisms of translational inhibition are different. Our results highlight an astonishing plasticity of mRNA in its ability to adapt to evolutionary constraints, that contrasts with the extreme conservation of the rRNA-binding site.
Serganov
Alexander
A
Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Polonskaia
Ann
A
Ehresmann
Bernard
B
Ehresmann
Chantal
C
Patel
Dinshaw J
DJ
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D014176:Protein Biosynthesis; D023302:Protein Footprinting; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D016963:Thermus thermophilus / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D012269:Ribosomal Proteins; C036004:ribosomal protein S15