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Adaptive Attenuation: An Iron-Depend...

Pokorzynski, Nicholas David.

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Adaptive Attenuation: An Iron-Dependent Transcriptional Repressor Functions as a Regulator and Biosensor of Tryptophan Levels in Chlamydia Trachomatis.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Adaptive Attenuation: An Iron-Dependent Transcriptional Repressor Functions as a Regulator and Biosensor of Tryptophan Levels in Chlamydia Trachomatis./
作者:	Pokorzynski, Nicholas David.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
面頁冊數:	399 p.
附註:	Source: Dissertations Abstracts International, Volume: 82-10, Section: B.
Contained By:	Dissertations Abstracts International82-10B.
標題:	Microbiology. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28152725
ISBN:	9798597009094

Adaptive Attenuation: An Iron-Dependent Transcriptional Repressor Functions as a Regulator and Biosensor of Tryptophan Levels in Chlamydia Trachomatis.
Pokorzynski, Nicholas David.

Adaptive Attenuation: An Iron-Dependent Transcriptional Repressor Functions as a Regulator and Biosensor of Tryptophan Levels in Chlamydia Trachomatis. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 399 p.

Source: Dissertations Abstracts International, Volume: 82-10, Section: B.

Thesis (Ph.D.)--Washington State University, 2020.

This item must not be sold to any third party vendors.

Nutritional immunity, whereby the host defensively starves invading pathogens of essential nutrients, can determine the outcome of host-pathogen interactions. During infection, the obligate intracellular bacterial pathogen Chlamydia trachomatis (Ctr) encounters environments with diverse nutrient availability. Normal chlamydial development depends on sufficient access to the biometal iron and the amino acid tryptophan, but both nutrients can be actively withheld by the host. Whereas many model bacteria elicit universal stress response mechanisms to survive varied nutritional insults, it is unclear the extent to which Ctr tailors its response to distinct stressors. Herein, we provide evidence for a regulatory circuit by which Ctr coordinates its stress responses to iron and tryptophan deprivation, through the iron-dependent transcriptional repressor, YtgR.Transcriptomic analyses following transient iron limitation initially revealed that Ctr independently induces expression of the tryptophan synthase genes, trpBA, within the trpRBA operon. Canonically repressed in a tryptophan-dependent manner by TrpR, TrpBA biosynthesize tryptophan from available indole, rendering them essential to counter host-mediated tryptophan starvation. Characterization of the iron-dependent cis- and trans-regulatory elements controlling trpBA expression indicated that YtgR represses trpRBA transcription, providing a mechanistic basis to iron-dependent trpBA regulation.Interestingly, YtgR is translationally fused to an N-terminal permease domain, YtgC, from which it is cleaved during infection. The YtgC domain encodes a rare motif of three sequential tryptophan residues (WWW), implicating tryptophan availability in the regulation of YtgR translation. Implementing genetic transformation of C. trachomatis, we observed WWW motif-dependent translational inhibition of YtgR following tryptophan deprivation. Thus, tryptophan availability dictates the extent of YtgR expression and thereby the level of iron-dependent repression of trpBA. The coupling of trpBA transcription to YtgR translation resembles tryptophan-dependent cis-attenuation of trp operons by TrpL in bacteria such as E. coli. Here, however, the signals are coupled by the trans-acting factor YtgR. We propose that this regulatory circuit evolved in adaptation to infection of the female lower genital tract, where microflora-derived indole provides the substrate for tryptophan salvage in an environment that is iron-restricted for Ctr. YtgR is thus poised as a critical regulator of the chlamydial stress response, warranting further studies of the scope of its regulatory activity.

ISBN: 9798597009094Subjects--Topical Terms:

536250
Microbiology.
Subjects--Index Terms:

Adaptive attenuation

Adaptive Attenuation: An Iron-Dependent Transcriptional Repressor Functions as a Regulator and Biosensor of Tryptophan Levels in Chlamydia Trachomatis.
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500 $a Source: Dissertations Abstracts International, Volume: 82-10, Section: B.
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520 $a Nutritional immunity, whereby the host defensively starves invading pathogens of essential nutrients, can determine the outcome of host-pathogen interactions. During infection, the obligate intracellular bacterial pathogen Chlamydia trachomatis (Ctr) encounters environments with diverse nutrient availability. Normal chlamydial development depends on sufficient access to the biometal iron and the amino acid tryptophan, but both nutrients can be actively withheld by the host. Whereas many model bacteria elicit universal stress response mechanisms to survive varied nutritional insults, it is unclear the extent to which Ctr tailors its response to distinct stressors. Herein, we provide evidence for a regulatory circuit by which Ctr coordinates its stress responses to iron and tryptophan deprivation, through the iron-dependent transcriptional repressor, YtgR.Transcriptomic analyses following transient iron limitation initially revealed that Ctr independently induces expression of the tryptophan synthase genes, trpBA, within the trpRBA operon. Canonically repressed in a tryptophan-dependent manner by TrpR, TrpBA biosynthesize tryptophan from available indole, rendering them essential to counter host-mediated tryptophan starvation. Characterization of the iron-dependent cis- and trans-regulatory elements controlling trpBA expression indicated that YtgR represses trpRBA transcription, providing a mechanistic basis to iron-dependent trpBA regulation.Interestingly, YtgR is translationally fused to an N-terminal permease domain, YtgC, from which it is cleaved during infection. The YtgC domain encodes a rare motif of three sequential tryptophan residues (WWW), implicating tryptophan availability in the regulation of YtgR translation. Implementing genetic transformation of C. trachomatis, we observed WWW motif-dependent translational inhibition of YtgR following tryptophan deprivation. Thus, tryptophan availability dictates the extent of YtgR expression and thereby the level of iron-dependent repression of trpBA. The coupling of trpBA transcription to YtgR translation resembles tryptophan-dependent cis-attenuation of trp operons by TrpL in bacteria such as E. coli. Here, however, the signals are coupled by the trans-acting factor YtgR. We propose that this regulatory circuit evolved in adaptation to infection of the female lower genital tract, where microflora-derived indole provides the substrate for tryptophan salvage in an environment that is iron-restricted for Ctr. YtgR is thus poised as a critical regulator of the chlamydial stress response, warranting further studies of the scope of its regulatory activity.
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