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BIOLOGICAL SCIENCES / MICROBIOLOGY
Proteomic identification of tmRNA substrates
Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802
Communicated by Robert T. Sauer, Massachusetts Institute of Technology, Cambridge, MA, August 26, 2007 (received for review July 14, 2007)
The tmRNA–SmpB system releases ribosomes stalled on truncated mRNAs and tags the nascent polypeptides to target them for proteolysis. In many species, mutations that disrupt tmRNA activity cause defects in growth or development. In Caulobacter crescentus cells lacking tmRNA activity there is a delay in the initiation of DNA replication, which disrupts the cell cycle. To understand the molecular basis for this phenotype, 73 C. crescentus proteins were identified that are tagged by tmRNA under normal growth conditions. Among these substrates, proteins involved in DNA replication, recombination, and repair were overrepresented, suggesting that misregulation of these factors in the absence of tmRNA activity might be responsible for the delay in initiation of DNA replication. Analysis of the tagging sites within these substrates revealed a conserved nucleotide motif 5' of the tagging site, which is required for wild-type tmRNA tagging.
bacterial cell cycle | proteolysis | trans-translation
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/cgi/content/full/0707671104/DC1.
*To whom correspondence should be addressed. E-mail: kkeiler{at}psu.edu
© 2007 by The National Academy of Sciences of the USA
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