Role of a Peptide Tagging System in Degradation of Proteins Synthesized from Damaged Messenger RNA

Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA.
Science (Impact Factor: 33.61). 03/1996; 271(5251):990-3. DOI: 10.1126/science.271.5251.990
Source: PubMed


Variants of lambda repressor and cytochrome b562 translated from messenger RNAs without stop codons were modified by carboxyl terminal addition of an ssrA-encoded peptide tag and subsequently degraded by carboxyl terminal-specific proteases present in both the cytoplasm and periplasm of Escherichia coli. The tag appears to be added to the carboxyl terminus of the nascent polypeptide chain by cotranslational switching of the ribosome from the damaged messenger RNA to ssrA RNA.

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    • "The relatively clear picture emerging from the in vitro studies is muddied somewhat by the complexity of tmRNA activity in vivo. When first describing the trans-translation model, Sauer proposed that ribosome stalling on non-stop mRNAs gives tmRNA increased opportunity to enter and recycle these complexes (Keiler et al., 1996). However, later studies seem to suggest that transtranslation can also occur at internal sites within intact mRNAs. "
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    • "Direct evidence for ribosome rescue activity of ArfA was obtained by using artificially constructed model gene which has intrinsic transcription terminator within its ORF. It produces non-stop mRNA in vivo (Keiler et al., 1996). NTC formed at the 3′-end of such non-stop model mRNA is resolved by trans-translation system and the translation product (non-stop polypeptide hereafter) is lead to rapid degradation because of the degradation tag at its C-terminus. "
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