hrcA, Encoding the Repressor of the groEL Genes in Streptomyces albus G, Is Associated with a Second dnaJ Gene

AUTOR(ES)

Grandvalet, Cosette

FONTE

American Society for Microbiology

RESUMO

Expression of the principal chaperones of the heat shock stimulon of Streptomyces albus G are under the negative control of different repressors. The dnaK operon is regulated by hspR, the last gene of the operon (dnaK-grpE-dnaJ-hspR). hsp18, encoding a member of the small heat shock protein family, is regulated by orfY, which is in the opposite orientation upstream of hsp18. The groES-groEL1 operon and the groEL2 gene are regulated differently. They present tandem copies of the CIRCE element found in the 5′ region of many heat shock genes and shown to act in Bacillus subtilis as an operator for a repressor encoded by hrcA (hrc stands for heat regulation at CIRCE). We report the identification in S. albus of a new heat shock operon containing hrcA and dnaJ homologs. Disruption of hrcA increased the transcription of the groES-groEL1 operon and of the groEL2 gene. These features were lost when the mutant was complemented in trans by an intact copy of hrcA. Despite considerable accumulation of the GroE chaperones in the hrcA mutant, there was no effect on formation of the aerial mycelium and sporulation, indicating that neither hrcA nor the level of groE gene expression is directly involved in the regulation of Streptomyces morphological differentiation.

Documentos Relacionados

• Renaturation of Bacillus thermoglucosidasius HrcA Repressor by DNA and Thermostability of the HrcA-DNA Complex In Vitro
• Characterization of the groEL-like genes in Streptomyces albus.
• hrcA, the first gene of the Bacillus subtilis dnaK operon encodes a negative regulator of class I heat shock genes.
• Identification of a Caulobacter crescentus operon encoding hrcA, involved in negatively regulating heat-inducible transcription, and the chaperone gene grpE.
• Genetic and Physiologic Analysis of the groE Operon and Role of the HrcA Repressor in Stress Gene Regulation and Acid Tolerance in Streptococcus mutans