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Journal of Bacteriology, July 1999, p. 4081-4088, Vol. 181, No. 13
Department of
Biochemistry1 and Genetics
Program,2 Michigan State University, East
Lansing, Michigan 48824
Received 5 February 1999/Accepted 20 April 1999
Temporal and spatial gene regulation during Bacillus
subtilis sporulation involves the activation and inactivation of
multiple sigma subunits of RNA polymerase in a cascade. In the mother
cell compartment of sporulating cells, expression of the
sigE gene, encoding the earlier-acting sigma factor,
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
K Can Negatively Regulate
sigE Expression by Two Different Mechanisms during
Sporulation of Bacillus subtilis
E, is negatively regulated by the later-acting sigma
factor,
K. Here, it is shown that the negative feedback
loop does not require SinR, an inhibitor of sigE
transcription. Production of
K about 1 h earlier
than normal does affect Spo0A, which when phosphorylated is an
activator of sigE transcription. A mutation in the
spo0A gene, which bypasses the phosphorelay leading to the
phosphorylation of Spo0A, diminished the negative effect of early
K production on sigE expression early in
sporulation. Also, early production of
K reduced
expression of other Spo0A-dependent genes but not expression of the
Spo0A-independent ald gene. In contrast, both
sigE and ald were overexpressed late in
development of cells that fail to make
K. The
ald promoter, like the sigE promoter, is
believed to be recognized by
A RNA polymerase,
suggesting that
K may inhibit
A activity
late in sporulation. To exert this negative effect,
K
must be transcriptionally active. A mutant form of
K
that associates with core RNA polymerase, but does not direct transcription of a
K-dependent gene, failed to
negatively regulate expression of sigE or ald
late in development. On the other hand, the negative effect of early
K production on sigE expression early in
sporulation did not require transcriptional activity of
K RNA polymerase. These results demonstrate that
K can negatively regulate sigE expression by
two different mechanisms, one observed when
K is
produced earlier than normal, which does not require
K
to be transcriptionally active and affects Spo0A, and the other observed when
K is produced at the normal time, which
requires
K RNA polymerase transcriptional activity. The
latter mechanism facilitates the switch from
E to
K in the cascade controlling mother cell gene expression.
*
Corresponding author. Mailing address: Department of
Biochemistry, Michigan State University, East Lansing, MI 48824. Phone: (517) 355-9726. Fax: (517) 353-9334. E-mail:
kroos{at}pilot.msu.edu.
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