Related Experiment Video
Updated: May 3, 2026
06:12
Production of Double-stranded DNA Ministrings
Published on: February 29, 2016
12.3K
Mini-P1 plasmid replication: the autoregulation-sequestration paradox.
D K Chattoraj1, R J Mason, S H Wickner
1Laboratory of Biochemistry, National Cancer Institute, Bethesda, Maryland 20892.
Cell
|February 26, 1988
Summary
Initiator protein RepA controls mini-P1 plasmid replication. DNA looping by RepA simultaneously binding the control locus and promoter resolves the autoregulation-sequestration paradox, enabling repression.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The initiator protein RepA is proposed as rate-limiting for mini-P1 plasmid replication.
- Plasmid copy number control is thought to sequester RepA, reducing replication.
- RepA autoregulation presents a paradox with sequestration, as lost protein should be replenished.
Purpose of the Study:
- To resolve the paradox between RepA autoregulation and sequestration in mini-P1 plasmid replication control.
- To investigate the mechanism by which sequestered RepA might still exert regulatory control.
Main Methods:
- Demonstration of RepA binding to both the control locus and promoter region.
- Observation of DNA looping induced by simultaneous RepA binding.
Main Results:
- RepA binds simultaneously to the mini-P1 plasmid control locus and promoter region.
- This simultaneous binding results in the looping of the intervening DNA.
- DNA looping provides a mechanism for RepA to exert repression.
Conclusions:
- RepA-mediated DNA looping resolves the autoregulation-sequestration paradox.
- Sequestered RepA remains available for promoter repression, not just replication.
- This mechanism explains how RepA controls plasmid copy number.
Related Concept Videos
02:37Restarting Stalled Replication Forks
5.1K
DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart,...
5.1K
01:58Prokaryotic Transcriptional Activators and Repressors
20.1K
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...
20.1K
01:29Coordination of Gene Expression Processes in Bacteria
1.1K
The DNA replication, transcription, and translation processes are intricately coupled in bacteria, allowing efficient gene expression and rapid protein synthesis. While this physical and functional coordination is advantageous, it introduces challenges that bacteria overcome through specific regulatory mechanisms.Coupling of Replication, Transcription, and TranslationThe coupling of replication, transcription, and translation is a hallmark of bacterial gene expression. As the replisome unwinds...
1.1K
01:23Operon Model
2.5K
The operon model represents a fundamental mechanism of gene regulation in prokaryotes, enabling coordinated expression of genes involved in related metabolic or functional pathways. Operons consist of structural genes, a promoter, and an operator, with transcription regulated by repressors, activators, and small effector molecules.Structure and Function of OperonsAn operon is a cluster of structural genes transcribed together under the control of a single promoter. The promoter region...
2.5K
01:21Repressible Operon: trp Operon
2.7K
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...
2.7K
01:23Stringent Response in E. coli
528
Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...
528