Cold-temperature induction of Escherichia coli polynucleotide phosphorylase occurs by reversal of its autoregulation.
When Escherichia coli cells are shifted to low temperatures (e.g. 15 degrees C), growth halts while the 'cold shock response' (CSR) genes are induced, after which growth resumes. One CSR gene, pnp, encodes polynucleotide phosphorylase (PNPase), a 3'-exoribonuclease and component of the RNA degradosome. At 37 degrees C, ribonuclease III (RNase III, encoded by rnc) cleaves the pnp untranslated leader, whereupon PNPase represses its own translation by an unknown mechanism. Here, we show that PNPase cold-temperature induction involves several post-transcriptional events, all of which require the intact pnp mRNA leader. The bulk of induction results from reversal of autoregulation at a step subsequent to RNase III cleavage of the pnp leader. We also found that pnp translation occurs throughout cold-temperature adaptation, whereas lacZ(+) translation was delayed. This difference is striking, as both mRNAs are greatly stabilized upon the shift to 15 degrees C. However, unlike the lacZ(+) mRNA, which remains stable during adaptation, pnp mRNA decay accelerates. Together with other evidence, these results suggest that mRNA is generally stabilized upon a shift to cold temperatures, but that a CSR mRNA-specific decay process is initiated during adaptation.
Beran
R K
RK
1602 Molecular Science, Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA.
Simons
R W
RW
D000220:Adaptation, Biological / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D003080:Cold Temperature; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005095:Exoribonucleases / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D011117:Polyribonucleotide Nucleotidyltransferase / Q000096:biosynthesis / Q000235:genetics*; D012323:RNA Processing, Post-Transcriptional; D020871:RNA Stability; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D020506:Untranslated Regions
D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D020506:Untranslated Regions; C062260:cold shock protein CS7.4, Bacteria; D011117:Polyribonucleotide Nucleotidyltransferase; D005095:Exoribonucleases; C022535:exoribonuclease II