The Crc and Hfq proteins of Pseudomonas putida cooperate in catabolite repression and formation of ribonucleic acid complexes with specific target motifs

Environ Microbiol. 2015 Jan;17(1):105-18. doi: 10.1111/1462-2920.12499. Epub 2014 Jun 2.

Abstract

The Crc protein is a global regulator that has a key role in catabolite repression and optimization of metabolism in Pseudomonads. Crc inhibits gene expression post-transcriptionally, preventing translation of mRNAs bearing an AAnAAnAA motif [the catabolite activity (CA) motif] close to the translation start site. Although Crc was initially believed to bind RNA by itself, this idea was recently challenged by results suggesting that a protein co-purifying with Crc, presumably the Hfq protein, could account for the detected RNA-binding activity. Hfq is an abundant protein that has a central role in post-transcriptional gene regulation. Herein, we show that the Pseudomonas putida Hfq protein can recognize the CA motifs of RNAs through its distal face and that Crc facilitates formation of a more stable complex at these targets. Crc was unable to bind RNA in the absence of Hfq. However, pull-down assays showed that Crc and Hfq can form a co-complex with RNA containing a CA motif in vitro. Inactivation of the hfq or the crc gene impaired catabolite repression to a similar extent. We propose that Crc and Hfq cooperate in catabolite repression, probably through forming a stable co-complex with RNAs containing CA motifs to result in inhibition of translation initiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism*
  • Catabolite Repression / genetics*
  • Gene Expression Regulation, Bacterial
  • Host Factor 1 Protein / metabolism*
  • Nucleotide Motifs
  • Pseudomonas putida / genetics*
  • Pseudomonas putida / metabolism
  • RNA, Bacterial / chemistry
  • RNA, Bacterial / metabolism*
  • RNA, Messenger / chemistry
  • RNA, Messenger / metabolism
  • RNA, Small Untranslated / metabolism
  • Repressor Proteins / metabolism*

Substances

  • Bacterial Proteins
  • Host Factor 1 Protein
  • RNA, Bacterial
  • RNA, Messenger
  • RNA, Small Untranslated
  • Repressor Proteins
  • crc protein, Pseudomonas