title: Transcription elongation factor GreA has functional chaperone activity.
abstract: BACKGROUND
  Bacterial GreA is an indispensable factor in the RNA polymerase elongation complex. It plays multiple roles in transcriptional elongation, and may be implicated in resistance to various stresses.
  
  
  RESULTS
  In this study, we show that Escherichia coli GreA inhibits aggregation of several substrate proteins under heat shock condition. GreA can also effectively promote the refolding of denatured proteins. These facts reveal that GreA has chaperone activity. Distinct from many molecular chaperones, GreA does not form stable complexes with unfolded substrates. GreA overexpression confers the host cells with enhanced resistance to heat shock and oxidative stress. Moreover, GreA expression in the greA/greB double mutant could suppress the temperature-sensitive phenotype, and dramatically alleviate the in vivo protein aggregation. The results suggest that bacterial GreA may act as chaperone in vivo.
  
  
  CONCLUSIONS
  These results suggest that GreA, in addition to its function as a transcription factor, is involved in protection of cellular proteins against aggregation.
authors.affiliation: National Engineering Laboratory for Industrial Enzymes, Institute of Microbiology, Chinese Academy of Science, Beijing, People's Republic of China.
authors.forename: Kun
authors.initials: K
authors.lastname: Li
authors.forename: Tianyi
authors.initials: T
authors.lastname: Jiang
authors.forename: Bo
authors.initials: B
authors.lastname: Yu
authors.forename: Limin
authors.initials: L
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Gao
authors.forename: Cuiqing
authors.initials: C
authors.lastname: Ma
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
authors.forename: Yanhe
authors.initials: Y
authors.lastname: Ma
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D011489:Protein Denaturation; D017510:Protein Folding; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C079668:GreA protein, E coli; D018832:Molecular Chaperones; D014157:Transcription Factors