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gene expression regulation
Molecular Biology, Human Health 9th Edition, the process of gene transcription and translation is also the process in which the genetic information carried by genes is expressed as phenotypes, including gene transcription into complementary RNA sequences, translation of mRNA into polypeptide chains, and assembly of polypeptide chains into final of protein products.
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gene expression regulation
- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
- Project Management Process Template
Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
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gene expression regulation
Basic concepts and features
Gene expression: The process of gene transcription and translation is also the process in which the genetic information carried by genes is expressed as phenotypes, including gene transcription into complementary RNA sequences, translation of mRNA into polypeptide chains, and assembly of polypeptide chains into final protein products.
Temporal specificity of gene expression
According to functional needs, the strict expression of a specific gene occurs in a certain time sequence.
Time specificity of gene expression in multicellular organisms, also known as stage specificity Time specificity of gene expression in multicellular organisms, also known as stage specificity
Spatial specificity of gene expression
During the growth and development of an individual, the same gene product may be expressed differently in different tissues or organs of the individual.
The basis for the differences in the same internal organs, tissues, and cells is specific gene expression or differential gene expression.
Diversity in the way genes are expressed
Housekeeping genes (basic genes): genes that are continuously expressed in almost all cells of an organism and are not easily affected by environmental conditions
Inducible genes: Under the stimulation of specific environmental signals, the corresponding genes are activated and the gene expression products increase.
Repressible genes: Under the stimulation of specific environmental signals, the corresponding genes are repressed and the gene expression products are reduced.
Coordinated expression: Under the control of a certain mechanism, a group of functionally related genes, regardless of their expression mode, must be coordinated and expressed together.
Gene expression is regulated by regulatory sequences and regulatory molecules
Cis-acting element: a regulatory sequence located on the same DNA strand as the coding sequence being regulated
Trans-acting factors: Some regulatory sequences that are far away from the regulated coding sequence produce expression products that regulate coding genes. There are two types of proteins and DNA.
Gene expression regulation presents multiple levels and complexity
Gene expression regulation is reflected in the entire process of gene expression, in which regulation at the transcription level plays a crucial role. Transcription initiation is the basic control point of gene expression.
Prokaryotic gene expression regulation
Characteristics of prokaryotic genome
①The prokaryotic genome is a closed circular DNA molecule with a superhelical structure
②There are few repetitive sequences in the genome
③ The structural genes encoding proteins are continuous genes, and most of them are single-copy genes, but the genes encoding rRNA are still multi-copy genes.
④The proportion of structural genes in the genome (about 50%) is much larger than that of the eukaryotic genome
⑤Many structural genes are arranged in operon units in the genome
⑥Transcription and translation are performed in the same space, and there is not much difference in time
The operon is the basic unit of transcriptional regulation of prokaryotic genes.
Polycistronic: mRNA that carries information encoding multiple polypeptide chains
Monocistronic: mRNA that carries the coding information for a single polypeptide chain
Regulatory sequences include promoters and operator elements
The promoter is the site where RNA polymerase binds and is a key component that determines gene expression efficiency.
Consensus sequence: some similar sequences found in specific regions of various prokaryotic gene promoter sequences, usually in the -10 and -35 regions upstream of the transcription start point
The consensus sequence determines the transcriptional activity of the promoter
Regulatory genes encode repressor proteins that can bind to operating elements. Repressor proteins can recognize and bind specific operating elements to inhibit gene transcription. All repressor proteins mediate negative regulation.
The lactose operon is a typical inducible regulator
Expression characteristics of lactose metabolism enzyme genes: When there is no lactose in the environment, these genes are in a closed state; only when there is lactose in the environment, these genes are induced to open.
Structure of the lactose operator
Structural gene Z: encoding β-galactosidase
Structural gene Y: encoding permease
Structural gene A: encoding acetyltransferase
Operator sequence O: binding repressor protein
Promoter P (has a CAP binding site upstream)
Regulatory gene I: has an independent promoter (PI) and encodes a repressor protein
The P sequence, O sequence and CAP binding site together constitute the regulatory region of the lactose operon.
The lactose operon is dually regulated by repressor protein and CAP
Negative regulation of Lac repressor protein
Positive regulation of CAP
co-regulation
The tryptophan operon inhibits gene expression through repression and attenuation.
The E. coli tryptophan operator is a repressor operon. When there is no tryptophan in the cell, the repressor protein cannot bind to the operator sequence, so the tryptophan operon is in an open state and the structural genes can be expressed. On the contrary, tryptophan acts as a corepressor to form a complex with the repressor protein and binds to On the operator sequence, close the tryptophan operon and stop expression of the enzyme used to synthesize tryptophan.
Transcriptional attenuation: enhances the closing of the tryptophan operon by promoting the termination of mRNA synthesis that has already begun to be transcribed
Prokaryotic gene expression is finely regulated at the translation level
Protein molecules bind to or around promoters to regulate themselves
Translation repression utilizes the binding of proteins to their own mRNA to regulate translation initiation.
Antisense RNA modulates translation initiation using complementary sequences that bind to the translation initiation site of the mRNA
Coding frequency of mRNA codons affects translation speed
Eukaryotic gene expression regulation
Characteristics of eukaryotic genomes
①Linear double-stranded DNA molecules with superhelical structure
②The eukaryotic genome is much larger than the prokaryotic genome
③Eukaryotic genome contains a large number of repetitive sequences
④The structural genes of eukaryotes are break genes
⑤Eukaryotes do not have operons, and the mRNA produced by transcription is monocistronic.
⑥Existence of chromatin structure
⑦Genetic information not only exists in nuclear DNA, but also in mitochondrial DNA
Regulation at the level of chromatin structure
Transcriptionally activated chromatin is extremely sensitive to nucleases
Histone changes in transcriptionally activated chromatin
Reduced CpG island methylation levels
Regulation of transcription initiation
Cis-acting elements are key regulatory sites for transcription initiation
1. The promoter provides the transcription initiation signal
A promoter is a sequence on a DNA molecule that mediates the binding of RNA polymerase and the formation of a transcription initiation complex.
(1) Class I promoter [GC box]: mainly starts genes encoding rRNA, including core promoter and upstream promoter elements
(2) Class II promoter [TATA box]: mainly starts encoding mRNA and snRNA
(3) Class III promoter: mainly starts encoding 5S rRNA, tRNA, U6snRNA, etc.
2. Enhancers enhance neighboring genes
Enhancers are homeopathic elements that can enhance the working efficiency of eukaryotic promoters. They are the most important regulatory sequences of eukaryotic genes and determine the expression level of each gene in the cell. It functions independently of the orientation of its position.
3. Silencers are negative regulatory elements
Silencers are specific DNA sequences that can inhibit gene transcription. When combined with some trans-acting factors, they inhibit gene transcription and silence the gene.
4. Insulators hinder the action of enhancers
Insulators are elements on the genome that play an important role in transcriptional regulation. They can block the effect of enhancers on promoters or protect genes from the influence of the nearby chromatin environment.
The assembly of the transcription initiation complex is the primary means of transcriptional regulation
Post-transcriptional regulation mainly affects the structure and function of eukaryotic mRNA
The stability of mRNA affects eukaryotic gene expression
The 5’-end cap structure can increase the stability of mRNA
The 3’-end poly(A) tail prevents mRNA degradation
Some non-coding small RNAs can cause post-transcriptional gene silencing
Alternative splicing of pre-mRNA can regulate eukaryotic gene expression
Eukaryotic gene expression can still be regulated during and after translation
Regulation of translation initiation factor activity mainly occurs through phosphorylation modification
RNA-binding proteins are involved in the regulation of translation initiation
Regulation of translation product levels and activities can rapidly regulate gene expression
The regulation of gene expression by small RNA is very complex
The role of long non-coding RNA in the regulation of gene expression cannot be ignored