This

research was supported by funding from the Westaim Corporation, GSI-IX chemical structure the Alberta Science and Research Authority (ASRA), the Canadian Institutes for Health Research and the Canadian Cystic Fibrosis Foundation. S.L. holds the Westaim-ASRA Chair in Biofilm Research. R.E.W.H. holds a Canada Research Chair. “
“Yersinia polynucleotide phosphorylase (PNPase), a 3′–5′ exoribonuclease, has been shown to affect growth during several stress responses. In Escherichia coli, PNPase is one of the subunits of a multiprotein complex known as the degradosome, but also has degradosome-independent functions. The carboxy-terminus of E. coli ribonuclease E (RNase E) serves as the scaffold upon which PNPase, enolase (a glycolytic enzyme), and RhlB helicase all have been shown to bind. In the yersiniae, only PNPase has thus far been shown to physically interact with RNase E. We show by bacterial two-hybrid and co-immunoprecipitation assays that RhlB and enolase also interact with RNase E. Interestingly, although PNPase is required for normal growth at cold temperatures, assembly of the yersiniae degradosome was not required. However, degradosome assembly was required for growth in the presence of reactive oxygen species. These data suggest

that while the Yersinia pseudotuberculosis PNPase plays see more a role in the oxidative stress response through a degradosome-dependent mechanism, PNPase’s role during cold stress is degradosome-independent. Like other closely related Gram-negative enteric pathogens, Yersinia pseudotuberculosis employs a type III secretion system (T3SS) to infect host cells, and polynucleotide phosphorylase (PNPase),

a phosphorolytic 3′–5′ exoribonuclease involved in RNA decay, is required for its optimal functioning (Rosenzweig et al., 2005, 2007). Furthermore, we (and others) have observed that PNPase is required for the cold-shock response and/or acclimation for a number of organisms including Yersinia pestis MRIP and Y. pseudotuberculosis (Rosenzweig et al., 2005, 2007), Escherichia coli (Jones et al., 1987; Mathy et al., 2001; Yamanak & Inouye, 2001; Polissi et al., 2003), and Yersinia enterocolitica (Goverde et al., 1998; Neuhaus et al., 2000; Neuhaus et al., 2003). Intriguingly, PNPase has been shown to physically interact with an essential endoribonuclease, RNase E, in both Escherichia coli (Carpousis et al., 1994; Vanzo et al., 1998; Khemici & Carpousis, 2004) and Y. pseudotuberculosis (Yang et al., 2008) forming a large multiprotein RNA surveillance/quality control complex termed the degradosome. However, the role of the degradosome in various yersiniae stress responses has not been well studied. RNase E, PNPase, RhlB RNA helicase and enolase have all been identified as components of the E. coli degradosome (Carpousis, 2002; Khemici & Carpousis, 2004; Lawal et al., 2010).