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Related Concept Videos

Prokaryotic Transcriptional Activators and Repressors01:58

Prokaryotic Transcriptional Activators and Repressors

The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
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Prokaryotic Transcriptional Activators and Repressors01:58

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The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
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Chromatin Position Affects Gene Expression02:35

Chromatin Position Affects Gene Expression

Chromatin is the massive complex of DNA and proteins packaged inside the nucleus. The complexity of chromatin folding and how it is packaged inside the nucleus greatly influences  access to genetic information. Generally, the nucleus' periphery is considered transcriptionally repressive, while the cell's interior is considered a transcriptionally active area. 
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Cis-regulatory Sequences02:02

Cis-regulatory Sequences

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Application of Biolayer Interferometry (BLI) for Studying Protein-Protein Interactions in Transcription
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DNA supercoiling-dependent gene regulation in Chlamydia.

Eike Niehus1, Eric Cheng, Ming Tan

  • 1Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA.

Journal of Bacteriology
|July 29, 2008
PubMed
Summary

DNA supercoiling regulates gene expression in Chlamydia. Midcycle promoters respond to supercoiling changes, correlating with DNA topology shifts during the Chlamydia developmental cycle.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Chlamydia's unusual developmental cycle involves temporal gene expression.
  • Mechanisms regulating this temporal gene expression are largely unknown.
  • DNA topology, specifically supercoiling, is a potential regulatory mechanism.

Purpose of the Study:

  • To investigate if DNA supercoiling regulates Chlamydia gene expression.
  • To determine the differential response of Chlamydial promoters to DNA supercoiling.
  • To correlate DNA supercoiling levels with the Chlamydial developmental cycle.

Main Methods:

  • In vitro testing of five Chlamydial promoters at varying superhelical densities.
  • Assaying superhelical density of the Chlamydial plasmid at different infection time points.

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Main Results:

  • Individual Chlamydial promoters exhibit differential responses to DNA supercoiling.
  • Midcycle gene promoters (ompA, pgk) showed significant regulation (>8-fold) by supercoiling.
  • Late transcript promoters (omcAB, hctA, ltuB) were less sensitive to supercoiling (<2.2-fold).
  • Chlamydial plasmid supercoiling peaked at midcycle (-0.07) and was relaxed early/late (-0.03).

Conclusions:

  • DNA supercoiling acts as a regulatory mechanism for Chlamydia gene expression.
  • Differential promoter sensitivity to supercoiling, coupled with varying supercoiling levels, explains temporal gene expression patterns.
  • This study provides evidence for DNA topology-driven regulation in Chlamydia's developmental cycle.