Affiliation:
1. Departamento de Bioquı́mica, Instituto de Quı́mica, Universidade de São Paulo, São Paulo, São Paulo 05599-970, Brazil
Abstract
ABSTRACT
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 ς
32
-like promoter and a CIRCE element. Overexpression of
C. crescentus
ς
32
gives rise to higher levels of GroEL and increased levels of the
groESL
transcript coming from the ς
32
-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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
32 articles.
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