Affiliation:
1. Department of Biochemistry, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854
Abstract
ABSTRACT
In
Escherichia coli
, the cold shock response is exerted upon a temperature change from 37°C to 15°C and is characterized by induction of several cold shock proteins, including polynucleotide phosphorylase (PNPase), during acclimation phase. In
E. coli
, PNPase is essential for growth at low temperatures; however, its exact role in this essential function has not been fully elucidated. PNPase is a 3′-to-5′ exoribonuclease and promotes the processive degradation of RNA. Our screening of an
E. coli
genomic library for an in vivo counterpart of PNPase that can compensate for its absence at low temperature revealed only one protein, another 3′-to-5′ exonuclease, RNase II. Here we show that the RNase PH domains 1 and 2 of PNPase are important for its cold shock function, suggesting that the RNase activity of PNPase is critical for its essential function at low temperature. We also show that its polymerization activity is dispensable in its cold shock function. Interestingly, the third 3′-to-5′ processing exoribonuclease, RNase R of
E. coli
, which is cold inducible, cannot complement the cold shock function of PNPase. We further show that this difference is due to the different targets of these enzymes and stabilization of some of the PNPase-sensitive mRNAs, like
fis
, in the Δ
pnp
cells has consequences, such as accumulation of ribosomal subunits in the Δ
pnp
cells, which may play a role in the cold sensitivity of this strain.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
42 articles.
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