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A complex control system for transcriptional activation from the sid promoter of bacteriophage P4.

ABSTRACT: The sid gene promoter (Psid), which controls expression of the late genes from satellite phage P4, is activated by a unique class of small DNA-binding proteins. The activators from both satellite and helper phages stimulate transcription from Psid. These activators bind to sites centered at position -55 in all the helper and satellite phage late promoters. P4 Psid is unique in that it has an additional activator binding site centered at position -18 (site II). We have constructed a mutant of site II that no longer binds activators. Transcription under the control of satellite phage activators is increased by the site II mutation. In contrast, helper phage activators do not show this increase in transcription from Psid mutated at site II. Competition gel shift analysis reveals that the P4 satellite phage activator, Delta, binds eightfold better to site II than to site I. The products of the sid transcription unit are needed only when a helper phage is present; thus, the satellite phage activators repress transcription until the helper is present to supply a nonrepressing activator.

SUBMITTER: Reiter K

PROVIDER: S-EPMC107552 | biostudies-literature | 1998 Oct

REPOSITORIES: biostudies-literature

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A complex control system for transcriptional activation from the sid promoter of bacteriophage P4.

Reiter K K Lam H H Young E E Julien B B Calendar R R

Journal of bacteriology 19981001 19

The sid gene promoter (Psid), which controls expression of the late genes from satellite phage P4, is activated by a unique class of small DNA-binding proteins. The activators from both satellite and helper phages stimulate transcription from Psid. These activators bind to sites centered at position -55 in all the helper and satellite phage late promoters. P4 Psid is unique in that it has an additional activator binding site centered at position -18 (site II). We have constructed a mutant of sit ...[more]

PMID: 9748449

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Project description:During late stages of cystic fibrosis pulmonary infections, Pseudomonas aeruginosa often overproduces the exopolysaccharide alginate, protecting the bacterial community from host immunity and antimicrobials. The transcription of the alginate biosynthesis operon is under tight control by a number of factors, including AmrZ, the focus of this study. Interestingly, multiple transcription factors interact with the far-upstream region of this promoter (PalgD), in which one AmrZ binding site has been identified previously. The mechanisms of AmrZ binding and subsequent activation remain unclear and require more-detailed investigation. In this study, in-depth examinations elucidated four AmrZ binding sites, and their disruption eliminated AmrZ binding and promoter activation. Furthermore, our in vitro fluorescence resonance energy transfer experiments suggest that AmrZ holds together multiple binding sites in PalgD and thereafter induces the formation of higher-order DNA-AmrZ complexes. To determine the importance of interactions between those AmrZ oligomers in the cell, a DNA phasing experiment was performed. PalgD transcription was significantly impaired when the relative phase between AmrZ binding sites was reversed (5 bp), while a full-DNA-turn insertion (10 bp) restored promoter activity. Taken together, the investigations presented here provide a deeper mechanistic understanding of AmrZ-mediated binding to PalgD IMPORTANCE: Overproduction of the exopolysaccharide alginate provides protection to Pseudomonas aeruginosa against antimicrobial treatments and is associated with chronic P. aeruginosa infections in the lungs of cystic fibrosis patients. In this study, we combined a variety of microbiological, genetic, biochemical, and biophysical approaches to investigate the activation of the alginate biosynthesis operon promoter by a key transcription factor named AmrZ. This study has provided important new information on the mechanism of activation of this extremely complex promoter.

Dataset Information

A complex control system for transcriptional activation from the sid promoter of bacteriophage P4.

Publications

A complex control system for transcriptional activation from the sid promoter of bacteriophage P4.

Similar Datasets

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