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J. Bacteriol., Aug 1995, 4645-4651, Vol 177, No. 16
P Gulati, D Xu and HB Kaplan
Developmental expression of the Myxococcus xanthus gene 4521 requires
extracellular A-signal. This signal is generated in response to nutrient
limitation and functions in cell density sensing. To identify the upstream
limit of the minimum region required in vivo for A-signal- dependent 4521
expression, a 5' deletion analysis of the 4521 regulatory region was
performed. A new vector, pHBK280, was designed to facilitate this analysis.
This vector creates tandem copies of the 4521 gene in the M. xanthus
chromosome, such that the regulatory region to be tested is upstream of a
single copy of the lacZ reporter gene. The 5' deletion analysis revealed
that at most, 146 bp of DNA upstream of the transcription start site (TSS)
was required for full developmental expression of 4521. Basal expression
levels were observed with constructions containing 90 bp of DNA upstream of
the TSS. In vitro gel retardation assays revealed that DNA fragments with
5' ends of 146 and 125 bp upstream of the TSS and a common 3' end of +24 bp
were retarded in their mobility after incubation with all of the M. xanthus
developmental crude cell extracts tested. In contrast, a fragment starting
at 90 bp upstream of the TSS and ending at +24 bp was not retarded in its
mobility after incubation with the same cell extracts. These in vivo and in
vitro data suggest that cis-acting elements located between 146 and 90 bp
upstream of the TSS serve as binding sites for one or more trans-acting
regulatory factors required for 4521 developmental expression.
Copyright © 1995, American Society for Microbiology
Identification of the minimum regulatory region of a Myxococcus xanthus A-signal-dependent developmental gene
Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston 77030, USA.
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