An RNA degradosome assembly in Caulobacter crescentus

In many bacterial species, the multi-enzyme RNA degradosome assembly makes key contributions to RNA metabolism. Powering the turnover of RNA and the processing of structural precursors, the RNA degradosome has differential activities on a spectrum of transcripts and contributes to gene regulation at a global level. Here, we report the isolation and characterization of an RNA degradosome assembly from the α-proteobacterium Caulobacter crescentus, which is a model organism for studying morphological development and cell-cycle progression. The principal components of the C. crescentus degradosome are the endoribonuclease RNase E, the exoribonuclease polynucleotide phosphorylase (PNPase), a DEAD-box RNA helicase and the Krebs cycle enzyme aconitase. PNPase and aconitase associate with specific segments in the C-terminal domain of RNase E that are predicted to have structural propensity. These recognition ‘microdomains’ punctuate structurally an extensive region that is otherwise predicted to be natively disordered. Finally, we observe that the abundance of RNase E varies through the cell cycle, with maxima at morphological differentiation and cell division. This variation may contribute to the program of gene expression during cell division.