The CIRCE Element and Its Putative Repressor Control Cell Cycle Expression of the Caulobacter crescentus groESL Operon

AUTOR(ES)

Baldini, Regina Lúcia

FONTE

American Society for Microbiology

RESUMO

The groESL operon is under complex regulation in Caulobacter crescentus. In addition to strong induction after exposure to heat shock, under physiological growth conditions, its expression is subject to cell cycle control. Transcription and translation of the groE genes occur primarily in predivisional cells, with very low levels of expression in stalked cells. The regulatory region of groESL contains both a ς32-like promoter and a CIRCE element. Overexpression of C. crescentus ς32 gives rise to higher levels of GroEL and increased levels of the groESL transcript coming from the ς32-like promoter. Site-directed mutagenesis in CIRCE has indicated a negative role for this cis-acting element in the expression of groESL only at normal growth temperatures, with a minor effect on heat shock induction. Furthermore, groESL-lacZ transcription fusions carrying mutations in CIRCE are no longer cell cycle regulated. Analysis of an hrcA null strain, carrying a disruption in the gene encoding the putative repressor that binds to the CIRCE element, shows constitutive synthesis of GroEL throughout the Caulobacter cell cycle. These results indicate a negative role for the hrcA gene product and the CIRCE element in the temporal control of the groESL operon.

Documentos Relacionados

• Cell cycle expression of the heat shock groESL operon in Caulobacter crescentus
• The groESL Chaperone Operon of Lactobacillus johnsonii†
• Cloning and characterization of two groESL operons of Rhodobacter sphaeroides: transcriptional regulation of the heat-induced groESL operon.
• Cloning and characterization of the groESL operon from Bacillus subtilis.
• Cloning, sequencing, and molecular analysis of the groESL operon of Clostridium acetobutylicum.