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Journal of Bacteriology, June 2005, p. 4149-4162, Vol. 187, No. 12
0021-9193/05/$08.00+0 doi:10.1128/JB.187.12.4149-4162.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
4406 Regulatory Region, a Developmental Promoter of Myxococcus xanthus, and a DNA Segment Responsible for Chromosomal Position-Dependent Inhibition of Gene Expression
,
Poorna Viswanathan,
Scott J. Nowak,
Monica Gloudemans, and
Lee Kroos*
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
Received 14 December 2004/ Accepted 4 March 2005
When starved, Myxococcus xanthus cells send signals to each other that coordinate their movements, gene expression, and differentiation. C-signaling requires cell-cell contact, and increasing contact brought about by cell alignment in aggregates is thought to increase C-signaling, which induces expression of many genes, causing rod-shaped cells to differentiate into spherical spores. C-signaling involves the product of the csgA gene. A csgA mutant fails to express many genes that are normally induced after about 6 h into the developmental process. One such gene was identified by insertion of Tn5 lac at site
4406 in the M. xanthus chromosome. Tn5 lac fused transcription of lacZ to the upstream
4406 promoter. In this study, the
4406 promoter region was identified by analyzing mRNA and by testing different upstream DNA segments for the ability to drive developmental lacZ expression in M. xanthus. The 5' end of
4406 mRNA mapped to approximately 1.3 kb upstream of the Tn5 lac insertion. A 1.0-kb DNA segment from 0.8 to 1.8 kb upstream of the Tn5 lac insertion, when fused to lacZ and integrated at a phage attachment site in the M. xanthus chromosome, showed a similar pattern of developmental expression as Tn5 lac
4406. The DNA sequence upstream of the putative transcriptional start site was strikingly similar to promoter regions of other C-signal-dependent genes. Developmental lacZ expression from the 1.0-kb segment was abolished in a csgA mutant but was restored upon codevelopment of the csgA mutant with wild-type cells, which supply C-signal, demonstrating that the
4406 promoter responds to extracellular C-signaling. Interestingly, the 0.8-kb DNA segment immediately upstream of Tn5 lac
4406 inhibited expression of a downstream lacZ reporter in transcriptional fusions integrated at a phage attachment site in the chromosome but not at the normal
4406 location. To our knowledge, this is the first example in M. xanthus of a chromosomal position-dependent effect on gene expression attributable to a DNA segment outside the promoter region.
J.L. and P.V. contributed equally to the work presented.
Present address: The Anthony Nolan Research Institute, The Royal Free and University College Medical School, London, United Kingdom.
Present address: Skirball Institute of Biomolecular Medicine, 540 First Avenue, New York, NY 10016.
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