Send to

Choose Destination
Mol Microbiol. 2000 Jun;36(6):1470-80.

Transcriptional and post-transcriptional control of polynucleotide phosphorylase during cold acclimation in Escherichia coli.

Author information

Centro di Studio del Consiglio Nazionale delle Ricerche sulla Biologia Cellulare e Molecolare delle Piante, c/o Dipartimento di Biologia, UniversitĂ  degli Studi di Milano, Italy.


Polynucleotide phosphorylase (PNPase, polyribonucleotide nucleotidyltransferase, EC is one of the cold shock-induced proteins in Escherichia coli and pnp, the gene encoding it, is essential for growth at low temperatures. We have analysed the expression of pnp upon cold shock and found a dramatic transient variation of pnp transcription profile: within the first hour after temperature downshift the amount of pnp transcripts detectable by Northern blotting increased more than 10-fold and new mRNA species that cover pnp and the downstream region, including the cold shock gene deaD, appeared; 2 h after temperature downshift the transcription profile reverted to a preshift-like pattern in a PNPase-independent manner. The higher amount of pnp transcripts appeared to be mainly due to an increased stability of the RNAs. The abundance of pnp transcripts was not paralleled by comparable variation of the protein: PNPase steadily increased about twofold during the first 3 h at low temperature, as determined both by Western blotting and enzymatic activity assay, suggesting that PNPase, unlike other known cold shock proteins, is not efficiently translated in the acclimation phase. In experiments aimed at assessing the role of PNPase in autogenous control during cold shock, we detected a Rho-dependent termination site within pnp. In the cold acclimation phase, termination at this site depended upon the presence of PNPase, suggesting that during cold shock pnp is autogenously regulated at the level of transcription elongation.

[Indexed for MEDLINE]
Free full text

Supplemental Content

Full text links

Icon for Wiley
Loading ...
Support Center