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Regulation of Gene Expression, Archaeal (n.)
1.(MeSH)Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in archaea.
Regulation of Gene Expression, Developmental (n.)
1.(MeSH)Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.
Regulation of Gene Expression, Embryologic (n.)
1.(MeSH)Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.
Regulation of Gene Expression, Plant (n.)
1.(MeSH)Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in plants.
Regulation of Gene Expression, Neoplastic (n.)
1.(MeSH)Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in neoplastic tissue.
Regulation of Gene Expression, Viral (n.)
1.(MeSH)Any of the processes by which cytoplasmic factors influence the differential control of gene action in viruses.
Regulation of Gene Expression, Fungal (n.)
1.(MeSH)Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in fungi.
Regulation of Gene Expression, Bacterial (n.)
1.(MeSH)Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.
Regulation of Gene Expression (n.)
1.(MeSH)Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action at the level of transcription or translation. These processes include gene activation and genetic induction.
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Regulation of Gene Expression (n.) (MeSH)
G05.315, Expression Regulation, Gene (MeSH), Gene Action Regulation (MeSH), Gene Activation (MeSH), Gene Expression Regulation (MeSH), Genetic Induction (MeSH), Induction, Genetic (MeSH), Regulation, Gene Action (MeSH), Regulation, Gene Expression (MeSH)
Regulation of Gene Expression, Archaeal (n.) (MeSH)
G05.315.290, Archaeal Gene Expression Regulation (MeSH), Gene Expression Regulation, Archaeal (MeSH), Regulation, Gene Expression, Archaeal (MeSH)
Regulation of Gene Expression, Bacterial (n.) (MeSH)
G05.315.300, Bacterial Gene Expression Regulation (MeSH), Gene Expression Regulation, Bacterial (MeSH), Regulation, Gene Expression, Bacterial (MeSH)
Regulation of Gene Expression, Developmental (n.) (MeSH)
G05.315.310, Developmental Gene Expression Regulation (MeSH), Embryologic Gene Expression Regulation (MeSH), Gene Expression Regulation, Developmental (MeSH), Gene Expression Regulation, Embryologic (MeSH), Regulation, Gene Expression, Developmental (MeSH), Regulation, Gene Expression, Embryologic (MeSH), Regulation of Gene Expression, Embryologic (MeSH)
Regulation of Gene Expression, Embryologic (n.) (MeSH)
G05.315.310, Developmental Gene Expression Regulation (MeSH), Embryologic Gene Expression Regulation (MeSH), Gene Expression Regulation, Developmental (MeSH), Gene Expression Regulation, Embryologic (MeSH), Regulation, Gene Expression, Developmental (MeSH), Regulation, Gene Expression, Embryologic (MeSH), Regulation of Gene Expression, Developmental (MeSH)
Regulation of Gene Expression, Fungal (n.) (MeSH)
G05.315.330, Fungal Gene Expression Regulation (MeSH), Gene Expression Regulation, Fungal (MeSH), Regulation, Gene Expression, Fungal (MeSH)
Regulation of Gene Expression, Neoplastic (n.) (MeSH)
G05.315.370, Gene Expression Regulation, Neoplastic (MeSH), Neoplastic Gene Expression Regulation (MeSH), Regulation, Gene Expression, Neoplastic (MeSH)
Regulation of Gene Expression, Plant (n.) (MeSH)
G05.315.375, Gene Expression Regulation, Plant (MeSH), Plant Gene Expression Regulation (MeSH), Regulation, Gene Expression, Plant (MeSH)
Regulation of Gene Expression, Viral (n.) (MeSH)
G05.315.385, Gene Expression Regulation, Viral (MeSH), Regulation, Gene Expression, Viral (MeSH), Viral Gene Expression Regulation (MeSH)
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Regulation of Gene Expression (n.) [MeSH]
Wikipedia
Regulation of gene expression (or gene regulation) includes the processes that cells and viruses use to regulate the way that the information in genes is turned into gene products. Although a functional gene product can be an RNA, the majority of known mechanisms regulate protein coding genes. Any step of the gene's expression may be modulated, from DNA-RNA transcription to the post-translational modification of a protein.
Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed. Although as early as 1951 Barbara McClintock showed interaction between two genetic loci, Activator (Ac) and Dissociator (Ds), in the color formation of maize seeds, the first discovery of a gene regulation system is widely considered to be the identification in 1961 of the lac operon, discovered by Jacques Monod, in which some enzymes involved in lactose metabolism are expressed by the genome of E. coli only in the presence of lactose and absence of glucose.
Furthermore, in multicellular organisms, gene regulation drives the processes of cellular differentiation and morphogenesis, leading to the creation of different cell types that possess different gene expression profiles, and hence produce different proteins/have different ultrastructures that suit them to their functions (though they all possess the genotype, which follows the same genome sequence).
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Any step of gene expression may be modulated, from the DNA-RNA transcription step to post-translational modification of a protein. The following is a list of stages where gene expression is regulated, the most extensively utilised point is Transcription Initiation:
In eukaryotes, the accessibility of large regions of DNA can depend on its chromatin structure, which can be altered as a result of histone modifications directed by DNA methylation, ncRNA, or DNA-binding protein. Hence these modifications may up or down regulate the expression of gene. Certain of these modifications that regulate gene expression are inheritable and are referred to as epigenetic regulation.
Methylation of DNA is a common method of gene silencing. DNA is typically methylated by methyltransferase enzymes on cytosine nucleotides in a CpG dinucleotide sequence (also called "CpG islands" when densely clustered). Analysis of the pattern of methylation in a given region of DNA (which can be a promoter) can be achieved through a method called bisulfite mapping. Methylated cytosine residues are unchanged by the treatment, whereas unmethylated ones are changed to uracil. The differences are analyzed by DNA sequencing or by methods developed to quantify SNPs, such as Pyrosequencing (Biotage) or MassArray (Sequenom), measuring the relative amounts of C/T at the CG dinucleotide. Abnormal methylation patterns are thought to be involved in oncogenesis.[1]
Transcription of DNA is dictated by its structure. In general, the density of its packing is indicative of the frequency of transcription. Octameric protein complexes called nucleosomes are responsible for the amount of supercoiling of DNA, and these complexes can be temporarily modified by processes such as phosphorylation or more permanently modified by processes such as methylation. Such modifications are considered to be responsible for more or less permanent changes in gene expression levels.[2]
Histone acetylation is also an important process in transcription. Histone acetyltransferase enzymes (HATs) such as CREB-binding protein also dissociate the DNA from the histone complex, allowing transcription to proceed. Often, DNA methylation and histone deacetylation work together in gene silencing. The combination of the two seems to be a signal for DNA to be packed more densely, lowering gene expression.[citation needed]
Regulation of transcription thus controls when transcription occurs and how much RNA is created. Transcription of a gene by RNA polymerase can be regulated by at least five mechanisms:
After the DNA is transcribed and mRNA is formed, there must be some sort of regulation on how much the mRNA is translated into proteins. Cells do this by modulating the capping, splicing, addition of a Poly(A) Tail, the sequence-specific nuclear export rates, and, in several contexts, sequestration of the RNA transcript. These processes occur in eukaryotes but not in prokaryotes. This modulation is a result of a protein or transcript that, in turn, is regulated and may have an affinity for certain sequences.
The translation of mRNA can also be controlled by a number of mechanisms, mostly at the level of initiation. Recruitment of the small ribosomal subunit can indeed be modulated by mRNA secondary structure, antisense RNA binding, or protein binding. In both prokaryotes and eukaryotes, a large number of RNA binding proteins exist, which often are directed to their target sequence by the secondary structure of the transcript, which may change depending on certain conditions, such as temperature or presence of a ligand (aptamer). Some transcripts act as ribozymes and self-regulate their expression.
A large number of studied regulatory systems come from developmental biology. Examples include:
Up-regulation is a process that occurs within a cell triggered by a signal (originating internal or external to the cell), which results in increased expression of one or more genes and as a result the protein(s) encoded by those genes. On the converse, down-regulation is a process resulting in decreased gene and corresponding protein expression.
Gene Regulation can be summarized by the response of the respective system:
In general, most experiments investigating differential expression used whole cell extracts of RNA, called steady-state levels, to determine which genes changed and by how much they did. These are, however, not informative of where the regulation has occurred and may actually mask conflicting regulatory processess (see post-transcriptional regulation), but it is still the most commonly analysed (QPCR and DNA microarray).
When studying gene expression, there are several methods to look at the various stages. In eukaryotes these include:
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