Related Experiment Video
Updated: Jul 2, 2026
08:35
Inducible and Reversible Dominant-negative (DN) Protein Inhibition
Published on: January 7, 2019
A conserved anti-repressor controls horizontal gene transfer by proteolysis.
Baundauna Bose1, Jennifer M Auchtung, Catherine A Lee
1Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Molecular Microbiology
|September 3, 2008
Summary
Mobile genetic elements like ICEBs1 use a unique anti-repressor, ImmA, for repressor ImmR degradation. This ImmA-dependent proteolysis is crucial for regulating gene transfer in bacteria.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- ICEBs1 is a mobile genetic element in Bacillus subtilis, functioning as a conjugative transposon.
- ICEBs1 gene expression, excision, and transfer are activated by the SOS response and RapI-PhrI system, which inactivate the ImmR repressor.
- While ImmR resembles phage repressors, its inactivation mechanism is distinct.
Purpose of the Study:
- To investigate the mechanism of ImmR inactivation in ICEBs1.
- To identify the role of ICEBs1-encoded proteins in repressor regulation.
- To explore the conservation of this regulatory mechanism in other mobile genetic elements.
Main Methods:
- Investigated ImmR inactivation in Bacillus subtilis.
- Coexpressed ImmA and ImmR in Escherichia coli.
- Incubated purified ImmA and ImmR proteins.
- Examined homologues in Bacillus subtilis phage phi105.
Main Results:
- ICEBs1 repressor inactivation requires the ICEBs1-encoded anti-repressor ImmA.
- ImmA mediates the degradation of ImmR in B. subtilis.
- Coexpression or co-incubation of ImmA and ImmR led to site-specific cleavage of ImmR.
- An ImmA homologue from phage phi105 is essential for inactivating its cognate ImmR homologue.
Conclusions:
- ImmA-dependent proteolysis of ImmR is a novel mechanism for repressor inactivation.
- This mechanism is likely conserved across various mobile genetic elements, including bacteriophages.
- ImmA-mediated degradation of repressors represents a conserved regulatory strategy for controlling horizontal gene transfer.
Related Concept Videos
01:58Prokaryotic 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.
Transcription of prokaryotic...
Transcription of prokaryotic...
01:58Prokaryotic 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.
Transcription of prokaryotic...
Transcription of prokaryotic...
01:21Repressible Operon: trp Operon
The trp operon in Escherichia coli exemplifies a repressible operon. It regulates the synthesis of tryptophan through repressor-mediated transcriptional control and attenuation. This dual regulatory mechanism ensures tryptophan biosynthesis occurs only when needed, conserving cellular resources.Structure of the trp OperonThe trp operon consists of five structural genes (trpE, trpD, trpC, trpB, and trpA) that encode enzymes for tryptophan biosynthesis. These genes are transcribed as a single...
01:27Horizontal Gene Transfer
Horizontal gene transfer (HGT) is a process where genetic material moves between organisms within the same generation, unlike vertical gene transfer, which occurs from parent to offspring. HGT plays a crucial role in microbial evolution, adaptation, and survival, particularly in shared environments like the human gut.Mobile genetic elements such as plasmids, prophages, integrons, insertion sequences, and transposons facilitate this process. HGT occurs through three primary mechanisms:...
01:16Transduction
Among the three main modes of HGT—transformation, conjugation, and transduction—transduction is unique in that it is mediated by bacteriophages, or bacterial viruses.Transduction occurs in two ways. Generalized transduction occurs during the lytic cycle of a bacteriophage infection. In this process, bacteriophages infect bacterial cells, replicate within them, and ultimately cause cell lysis, releasing newly assembled virions. Occasionally, random fragments of the bacterial genome are...
02:18Types of Genetic Transfer Between Organisms
Genetic transfer occurs when genetic information is passed from one organism to another. It occurs via two mechanisms: vertical gene transfer and horizontal gene transfer. Vertical gene transfer occurs when genetic information is transferred from one generation to the next, which happens much more frequently than horizontal gene transfer. Both sexual and asexual reproduction are forms of vertical gene transfer, where one or more organisms pass some or all of their genome onto their progeny.