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J. Bacteriol., Apr 1995, 2107-2117, Vol 177, No. 8
JW Chung, BA Bensing and GM Dunny
The prgB gene encodes the surface protein Asc10, which mediates cell
aggregation resulting in high-frequency conjugative transfer of the
pheromone-inducible tetracycline resistance plasmid pCF10 in Enterococcus
faecalis. Previous Tn5 insertional mutagenesis and sequencing analysis of a
12-kb fragment of pCF10 indicated that a region containing prgX, -Q, -R,
-S, and -T, located 3 to 6 kb upstream of prgB, is required to activate the
expression of prgB. Complementation studies showed that the positive
regulatory region functions in cis in an orientation-dependent manner (J.
W. Chung and G. M. Dunny, Proc. Natl. Acad. Sci. USA 89:9020-9024, 1992).
In order to determine the involvement of each gene in the activation of
prgB, Tn5 insertional mutagenesis and exonuclease III deletion analyses of
the regulatory region were carried out. The results indicate that prgQ and
- S are required for the expression of prgB, while prgX, -R, and -T are not
required. Western blot (immunoblot) analysis of these mutants shows that
prgQ is also essential for the expression of prgA (encoding the surface
exclusion protein Sec10), which is located between prgB and the
positive-control region. Complementation analysis demonstrates that a
cis-acting regulatory element is located in the prgQ region and that pCF10
sequences in an untranslated region 3' from prgQ are an essential component
of the positive-control system. Analyses of various Tn5 insertions in pCF10
genes suggest that transcription reading into this transposon is terminated
in E. faecalis but that outward-reading transcripts may initiate from
within the ends of Tn5 or from the junction sequences.
Copyright © 1995, American Society for Microbiology
Genetic analysis of a region of the Enterococcus faecalis plasmid pCF10 involved in positive regulation of conjugative transfer functions
Institute for Advanced Studies in Biological Process Technology, University of Minnesota, St. Paul 55108, USA.
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