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. 2015 Oct;197(20):3238-44.
doi: 10.1128/JB.00379-15. Epub 2015 Jul 27.

Chlamydia trachomatis Type III Secretion Proteins Regulate Transcription

Brett R Hanson  1 , Anatoly Slepenkin  2 , Ellena M Peterson  2 , Ming Tan  3
Affiliations

Chlamydia trachomatis Type III Secretion Proteins Regulate Transcription

Brett R Hanson et al. J Bacteriol. 2015 Oct.

Abstract

The Scc4 protein (CT663) of the pathogenic bacterium Chlamydia has been described as a type III secretion (T3S) chaperone as well as an inhibitor of RNA polymerase. To examine if these roles are connected, we first investigated physical interactions between Chlamydia trachomatis Scc4 and the T3S chaperone Scc1 and a T3S substrate, CopN. In a yeast 3-hybrid assay, Scc4, Scc1, and CopN were all required to detect an interaction, which suggests that these proteins form a trimolecular complex. We also detected interactions between any two of these three T3S proteins in a pulldown assay using only recombinant proteins. We next determined whether these interactions affected the function of Scc4 as an inhibitor of RNA transcription. Using Escherichia coli as a heterologous in vivo system, we demonstrated that expression of C. trachomatis Scc4 led to a drastic decrease in transcript levels for multiple genes. However, coexpression of Scc4 with Scc1, CopN, or both alleviated Scc4-mediated inhibition of transcription. Scc4 expression also severely impaired E. coli growth, but this growth defect was reversed by coexpression of Scc4 with Scc1, CopN, or both, suggesting that the inhibitory effect of Scc4 on transcription and growth can be antagonized by interactions between Scc4, Scc1, and CopN. These findings suggest that the dual functions of Scc4 may serve as a bridge to link T3S and the regulation of gene expression in Chlamydia.

Importance: This study investigates a novel mechanism for regulating gene expression in the pathogenic bacterium Chlamydia. The Chlamydia type III secretion (T3S) chaperone Scc4 has been shown to inhibit transcription by RNA polymerase. This study describes physical interactions between Scc4 and the T3S proteins Scc1 and CopN. Furthermore, Chlamydia Scc1 and CopN antagonized the inhibitory effects of Scc4 on transcription and growth in a heterologous Escherichia coli system. These results provide evidence that transcription in Chlamydia can be regulated by the T3S system through interactions between T3S proteins.

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Figures

FIG 1
FIG 1
Pulldown assay showing protein-protein interactions for His-tagged Scc4 and Scc1 (rScc4 and rScc1) and native CopN. Lane 1 shows CopN present in the C. trachomatis lysate used in the pulldown assay (input). Lanes 2 to 4 show proteins recovered from the pulldown when the chlamydial lysate was incubated with cobalt resin and with rScc1 alone (lane 2), rScc4 alone (lane 3), or rScc1 and rScc4 (lane 4). Mouse polyclonal antibodies used to detect the proteins in the Western blot shown are as follows: lane 1, anti-His-CopN; and lanes 2 to 4, an antibody cocktail composed of anti-His-CopN, anti-His-Scc1, and anti-His-Scc4.
FIG 2
FIG 2
Effect of C. trachomatis Scc4, Scc1, and CopN in various combinations on the transcription of three E. coli genes. Transcripts were measured by qRT-PCR 4 h after expression of the chlamydial proteins was induced by IPTG. For each combination of chlamydial proteins, transcript levels were normalized to genome copy number and reported as a fold change from transcript levels in uninduced cells. Scc4 expression decreased transcription relative to that under all other experimental conditions (P < 0.05).
FIG 3
FIG 3
Effect of C. trachomatis Scc4, Scc1, and CopN in various combinations on E. coli growth as measured by OD600. Each graph shows the growth curve in the absence (uninduced) or presence (induced) of IPTG. The x axis shows the time after the addition of 0.1 mM IPTG to the induced sample. (A) Empty vector plasmid; (B) Scc1 and CopN; (C) Scc4 alone; (D) Scc4 and Scc1; (E) Scc4 and CopN; (F) Scc4, Scc1, and CopN.
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References

    1. Batteiger BE, Tan M. 2014. Chlamydia trachomatis (trachoma, genital infections, perinatal infections, and lymphogranuloma venereum), p 2154–2170. In Bennett JE, Dolin R, Mandell GL (ed), Mandell, Douglas, and Bennett's principles and practice of infectious diseases, 8th ed Elsevier Inc, Philadelphia, PA.
    1. Adams DA, Jajosky RA, Ajani U, Kriseman J, Sharp P, Onwen DH, Schley AW, Anderson WJ, Grigoryan A, Aranas AE, Wodajo MS, Abellera JP, Centers for Disease Control and Prevention (CDC). 2014. Summary of notifiable diseases—United States, 2012. MMWR Morb Mortal Wkly Rep 61:1–121. - PubMed
    1. Burton MJ, Mabey DC. 2009. The global burden of trachoma: a review. PLoS Negl Trop Dis 3:e460. doi:10.1371/journal.pntd.0000460. - DOI - PMC - PubMed
    1. Moulder JW. 1991. Interaction of Chlamydiae and host cells in vitro. Microbiol Rev 55:143–190. - PMC - PubMed
    1. Galán JE, Lara-Tejero M, Marlovits TC, Wagner S. 2014. Bacterial type III secretion systems: specialized nanomachines for protein delivery into target cells. Annu Rev Microbiol 68:415–438. doi:10.1146/annurev-micro-092412-155725. - DOI - PMC - PubMed

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