Name: how prokaryotic gene regulators work
Uploaded: 2023-04-30T18:28:46.000Z
Duration: 1 min 58 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.B.1.2

prokaryotic-transcriptional-activators-and-repressors

Prokaryotic Transcriptional Activators and Repressors

Prokaryotes contain a circular genome where, in many cases, related genes for certain biochemical processes are located directly adjacent to each other in the DNA sequence.&#160;&#160;
These gene clusters, known as operons, have a single promoter and are transcribed into a single mRNA.&#160; Expression of an operon is controlled by activators and repressors, proteins that promote or suppress transcription, respectively.&#160;&#160;
An activator binds to a promoter, leading to the binding of RNA polymerase and the subsequent transcription of an operon.
A repressor interacts with a different DNA sequence located in the vicinity of the promoter, known as the operator. When a repressor binds to the operator, it prevents RNA polymerase from binding to the promoter, inhibiting transcription.
Prokaryotic gene regulation is often dependent on nutrient availability.&#160; In some bacteria when glucose concentrations are low, it leads to the accumulation of cyclic AMP.&#160;
Cyclic AMP binds to an activator, the catabolite activator protein, and together they bind to a promoter. This initiates the expression of the lac operon, an operon containing genes that allow the bacteria to metabolize sugars other than glucose.
Tryptoph

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.
Transcription of prokaryotic genes in an operon is regulated by two types of DNA binding proteins known as activators and repressors. Activators bind to the promoter, the site of transcription initiation, and aid in the binding of RNA polymerase, the key enzyme involved in transcription.&#160; Repressors bind to operators, short regulatory sequences in the operon between the promoter and the genes, and inhibit the binding of RNA polymerase to the promoter.
A structural pre-requisite for activators and promoters is that they should be able to exist in two alternate conformations, one where they can bind to the DNA and one where they cannot. Another characteristic feature specific to activators is that they have two binding surfaces to simultaneously bind to both RNA polymerase and DNA. This recruitment of the two molecules brings the polymerase closer to the promoter and aids in its binding. Activators have no catalytic role to play in transcription and their function is limited to facilitating the binding of the enzyme and DNA. In the absence of an activator, RNA polymerase can still bind to DNA and show low levels of expression. If a repressor is present in this system, then the basal expression of that gene is prevented.
Regulation of the expression of prokaryotic genes is largely dependent on the nutrient availability and requirements of the organisms. These nutrients control the binding of activators and repressors to the operon and ensure that only the required set of genes is expressed. For example, the presence of tryptophan in a cell leads to its binding to a repressor which prevents the transcription of the trp operon and subsequent production of tryptophan.

The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes ...

Education

JoVE Core

Cell Biology

Unit 1

Control of Gene Expression

KEY TERMS AND CONCEPTS

how prokaryotic gene regulators work

Prokaryotic gene regulators control transcription by helping or blocking RNA polymerase. Activators and repressors are two main types of regulatory proteins that influence whether a gene is expressed. These proteins let bacteria adjust gene activity in response to changing conditions.

Activators help transcription start. They bind to specific DNA sequences near a promoter, which is the region where RNA polymerase begins transcription. By making RNA polymerase bind more easily, activators increase transcription of the target gene.

Repressors have the opposite effect. They also bind to specific DNA sequences near a promoter. When a repressor is bound, it can prevent RNA polymerase from starting transcription, which lowers or stops gene expression.

Together, activators and repressors give prokaryotes a way to fine-tune gene expression. This control helps cells respond quickly to environmental changes and manage when certain genes are turned on or off.

How Prokaryotic Gene Regulators Work

cell specific gene expression

Cell-Specific Gene Expression in Development

Cell-specific gene expression helps explain how different cells make different proteins, even when they contain the same DNA. This process is central to development and to the way specialized tissues form. Gene expression is controlled by regulatory signals that turn particular genes on or off in specific cells. As a result, one cell can follow a different molecular program from another cell in the same organism. These differences help create the variety of cell types needed for normal...

regulation of expression occurs at multiple steps

regulation-of-expression-occurs-at-multiple-steps

Gene Expression Control at Every Stage

Gene expression control happens at several stages. Cells can change when a gene is active and how much product it makes. This regulation helps the cell respond to changing needs. One major control point is transcription. In eukaryotes, transcription can be regulated before it starts. It can also be regulated while it is already underway. These steps help determine whether a gene is copied into RNA. Cells can also regulate expression after transcription. The RNA may be processed, moved, or...

cis-regulatory sequences

DNA Switches That Control Gene Expression

Cis-regulatory sequences are DNA switches that help control gene expression. They do not code for proteins. Instead, they can turn nearby genes on or off and help determine when a gene is active. These sequences include promoters and enhancers. They are often found near the genes they regulate, and their effect depends on where they are in the genome. Because they work through DNA itself, they help cells control which genes are used in different situations. Cis-regulatory sequences are an...

cooperative binding of transcription regulators

cooperative-binding-of-transcription-regulators

How Transcription Regulators Work Together

Transcription regulators can bind cooperatively to control gene expression. In cooperative binding, the binding of one regulator can make it easier for another regulator to bind nearby DNA. This shared effect helps cells fine-tune when genes are turned on or off. The topic also connects to how regulators interact with each other and with DNA. These interactions can strengthen binding at a target site. They can also change how strongly a gene is controlled in a specific cell or condition. <br...

Prokaryotic gene regulators control transcription by helping or blocking RNA polymerase. Activators and repressors are two main types of regulatory proteins that influence whether a gene is expressed. These proteins let bacteria adjust gene activity in response to changing conditions. Activators help transcription start. They bind to specific DNA sequences near a promoter, which is the region where RNA polymerase begins transcription. By making RNA polymerase bind more easily, activators...

the eukaryotic promoter region

Promoter Sequences in Eukaryotes

Eukaryotic promoter sequences control where transcription begins. A promoter is a DNA region that helps start gene expression. In eukaryotes, this region is usually found upstream of the gene it regulates. The promoter contains specific DNA sequences that can bind proteins needed for transcription. These sequences help position RNA polymerase at the correct start site. They also help determine whether a gene is turned on at the right time and in the right cell type. Eukaryotic promoters can...

co-activators and co-repressors

Gene Regulation by Co-activators and Co-repressors

Co-activators and co-repressors help control gene expression. They do not usually bind DNA themselves. Instead, they work with transcription factors to change how strongly a gene is turned on or off. Co-activators support transcription. They help transcription factors and RNA polymerase work together, which can increase gene expression. Co-repressors do the opposite. They help reduce transcription and lower gene expression. These proteins are important because cells need precise control over...

master transcription regulators

Master Transcription Regulators in Gene Control

Master transcription regulators help control when genes turn on and off. These proteins sit at the top of gene regulation networks and shape how cells respond to signals. In many cases, they act early in development and influence which cell types form. These regulators bind DNA and affect transcription, which is the first step in making RNA from a gene. By turning transcription on or off, they can change the levels of many downstream genes at once. That broad effect makes them important for...

regulated mrna transport

mRNA Localization During Cell Control

mRNA localization helps cells move messenger RNA to specific places before proteins are made. This process is regulated, so the cell can control when and where a protein is produced. Messenger RNA, or mRNA, carries genetic instructions from DNA to the protein-making machinery. By transporting mRNA to a defined location, a cell can keep protein production focused where it is needed most. Regulated mRNA transport is an important part of this control. It links the movement of RNA with later...

mrna stability and gene expression

mRNA Degradation and Protein Output

mRNA degradation helps control how much protein a cell makes. Messenger RNA, or mRNA, carries the genetic message from DNA to the ribosome, where proteins are built. When mRNA stays intact longer, it can be used more often. When it breaks down faster, protein production drops. Cells regulate mRNA stability with cis-acting elements. These are sequences within the mRNA itself that influence how long the message lasts. They can affect whether the mRNA is protected or targeted for decay. This...

micrornas

How miRNA Silences Genes

MicroRNA (miRNA) is a short regulatory RNA that helps control gene expression. It is transcribed from introns, which are non-coding parts of a gene, or from intergenic regions, which are stretches of DNA between genes. miRNA begins as a longer primary transcript and must go through several processing steps before it becomes active. The first transcript, called primary miRNA or pri-mRNA, folds back on itself to form a stem-loop structure. In the nucleus, the endonuclease Drosha shortens this...

small interfering rnas (sirna)

siRNA in Gene Silencing

Small interfering RNA, or siRNA, is a short RNA molecule that helps silence genes. It works after a gene has been copied into RNA, making it part of post-transcriptional gene silencing. Scientists study siRNA because it shows how cells can control which genetic messages are used. siRNA acts by guiding the cell to destroy a matching RNA message. This lowers the amount of protein that can be made from that message. The process is specific, because the siRNA must match the target RNA sequence...

lncrna - long non-coding rnas

Long Non-coding RNAs in Cell Control

Long non-coding RNAs, or lncRNAs, are RNA molecules that do not code for proteins. Instead, they can help control how genes are used in cells. This makes them important regulators of cell behavior. lncRNAs can work in several ways. Some influence chromatin modification, which changes how tightly DNA is packed and how easy it is for genes to be turned on or off. Others help guide the process of cell differentiation, when unspecialized cells develop into more specific cell types. Because of...

epigenetic regulation

DNA Methylation and X Inactivation

DNA methylation and X-chromosome inactivation help control which genes are turned on or off. These epigenetic changes alter the physical structure of DNA without changing the DNA sequence. They help each cell make only the proteins it needs. For example, bone growth proteins are not made in muscle cells. Epigenetic control is important for normal development. It also helps cells keep the right patterns of gene activity. When these controls fail, diseases can develop. Cancer is one example, but...

key terms and concepts

Learn how activators and repressors control transcription in prokaryotes by helping or blocking RNA polymerase at promoter sites.

How Prokaryotic Gene Regulators Work | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

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Endoplasmic Reticulum

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overview-of-myosin-structure-and-function

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1. Engage in evidence-based argument to relate a cell's function to the structure, function, and diversity of its components. Examples: Muscle cells have a large number of mitochondria, which create energy for contraction in the form of ATP. Some plant cells have a large vacuole which is used for storage and transport of excess nutrients in changing environments.

9-12.B.1.1

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Bacterial RNA Polymerase

Eukaryotic RNA Polymerases

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RNA Polymerase II Accessory Proteins

Transcription Elongation Factors

pre-mrna-processing-modification-of-pre-mrna-ends

Pre-mRNA Processing: Modification of pre-mRNA Ends

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Pre-mRNA Processing: RNA Splicing

Chromatin Structure and RNA Splicing

Alternative RNA Splicing

Nuclear Export of mRNA

Transfer RNA Synthesis

Ribosomal RNA Synthesis

The Nucleolus

Additional Subnuclear Structures

Translation

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tRNA Activation

Initiation of Translation

Termination of Translation

Improving Translational Accuracy

Nonsense-mediated mRNA Decay

The Eukaryotic Promoter Region

Molecular Chaperones and Protein Folding

Co-activators and Co-repressors

The Proteasome

Master Transcription Regulators

Regulated Protein Degradation

Regulated mRNA Transport

Proteins: From Genes to Degradation

mRNA Stability and Gene Expression

Cell Specific Gene Expression

MicroRNAs

MicroRNA (miRNA) are short, regulatory RNA transcribed from introns (non-coding regions of a gene) or intergenic regions (stretches of DNA present between ...

Regulation of Expression Occurs at Multiple Steps

Small interfering RNAs (siRNA)

Cis-regulatory Sequences

lncRNA - Long Non-coding RNAs

Cooperative Binding of Transcription Regulators

Epigenetic Regulation

Epigenetic changes alter the physical structure of the DNA without changing the genetic sequence and often regulate whether genes are turned on or off. ...

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9-12.B.1.2.a

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9-12.B.1.2.b

Recombinant DNA

Bacterial Transformation

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9-12.B.1.2.c

How Prokaryotic Gene Regulators Work

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