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Retinoic Acid Receptor
The retinoic acid receptor (RAR) is a type of nuclear receptor which can also act as a ligand-activated transcription factor that is activated by both all-trans retinoic acid and 9-cis retinoic acid the retinoid active derivatives of Vitamin A . They are typically found within the nucleus. There are three retinoic acid receptors (RAR), RAR-alpha, RAR-beta, and RAR-gamma, encoded by the , , genes, respectively. Within each RAR subtype there are various isoforms differing in their N-terminal region A. Multiple splice variants have been identified in human RARs: four for , five for , and two for . As with other type II nuclear receptors, RAR heterodimerizes with RXR and in the absence of ligand, the RAR/RXR dimer binds to hormone response elements known as retinoic acid response elements (RAREs) complexed with corepressor protein. Binding of agonist ligands to RAR results in dissociation of corepressor and recruitment of coactivator protein that, in turn, promotes transc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinoic Acid Receptor Alpha
Retinoic acid receptor alpha (RAR-α), also known as NR1B1 (nuclear receptor subfamily 1, group B, member 1) is a nuclear receptor that in humans is encoded by the ''RARA'' gene. NR1B1 is a gene with a protein product and has a chromosomal location of 17q21.2. RARA codes for the nuclear hormone receptor Retinoic Acid Receptor, Alpha subtype, and are themselves transcription factors. There are another 2 subtypes of RARs, Beta subtype, and Gamma subtype. Function Retinoid signaling is transduced by 2 families of nuclear receptors, retinoic acid receptor (RAR) and retinoid X receptor ( RXR), which form RXR/RAR heterodimers. In the absence of ligand, DNA-bound RXR/RARA represses transcription by recruiting the corepressors NCOR1, SMRT ( NCOR2), and histone deacetylase. When ligand binds to the complex, it induces a conformational change allowing the recruitment of coactivators, histone acetyltransferases, and the basic transcription machinery. Retinoic Acid Receptor Alpha, the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coactivator (genetics)
A coactivator is a type of transcriptional coregulator that binds to an activator (a transcription factor) to increase the rate of transcription of a gene or set of genes. The activator contains a DNA binding domain that binds either to a DNA promoter site or a specific DNA regulatory sequence called an enhancer. Binding of the activator-coactivator complex increases the speed of transcription by recruiting general transcription machinery to the promoter, therefore increasing gene expression. The use of activators and coactivators allows for highly specific expression of certain genes depending on cell type and developmental stage. Some coactivators also have histone acetyltransferase (HAT) activity. HATs form large multiprotein complexes that weaken the association of histones to DNA by acetylating the N-terminal histone tail. This provides more space for the transcription machinery to bind to the promoter, therefore increasing gene expression. Activators are found in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinoid Receptor
Retinoid receptors are nuclear receptors (a class of proteins) that bind to retinoids. When bound to a retinoid, they act as transcription factors, altering the expression of genes with corresponding response elements. Significant age-related declines in the levels of retinoid receptors in the forebrains of rats have been reversed by supplementation with the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which can restore neurogenesis. Subtypes include: * Retinoic acid receptor The retinoic acid receptor (RAR) is a type of nuclear receptor which can also act as a ligand-activated transcription factor that is activated by both all-trans retinoic acid and 9-cis retinoic acid the retinoid active derivatives of Vitamin A ...s (RARs) * Retinoid X receptors (RXRs) * RAR-related orphan receptors (RORs) References {{DEFAULTSORT:Retinoid Receptor Intracellular receptors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ubiquitin Proteasome Pathway
Proteasomes are protein complexes which degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds. Enzymes that help such reactions are called proteases. Proteasomes are part of a major mechanism by which cells regulate the concentration of particular proteins and degrade misfolded proteins. Proteins are tagged for degradation with a small protein called ubiquitin. The tagging reaction is catalyzed by enzymes called ubiquitin ligases. Once a protein is tagged with a single ubiquitin molecule, this is a signal to other ligases to attach additional ubiquitin molecules. The result is a ''polyubiquitin chain'' that is bound by the proteasome, allowing it to degrade the tagged protein. The degradation process yields peptides of about seven to eight amino acids long, which can then be further degraded into shorter amino acid sequences and used in synthesizing new proteins. Proteasomes are found inside all eukaryotes and archaea, and in some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Methylation
DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter, DNA methylation typically acts to repress gene transcription. In mammals, DNA methylation is essential for normal development and is associated with a number of key processes including genomic imprinting, X-chromosome inactivation, repression of transposable elements, aging, and carcinogenesis. As of 2016, two nucleobases have been found on which natural, enzymatic DNA methylation takes place: adenine and cytosine. The modified bases are N6-methyladenineD. B. Dunn, J. D. Smith: ''The occurrence of 6-methylaminopurine in deoxyribonucleic acids.'' In: ''Biochem J.'' 68(4), Apr 1958, S. 627–636. PMID 13522672. ., 5-methylcytosineB. F. Vanyushin, S. G. Tkacheva, A. N. Belozersky: ''Rare bases in animal DNA.'' In: ''Nature.'' 225, 1970, S. 948–949. PMID 4391887. and N4 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during the process of transcription, where an enzyme ( RNA polymerase) converts the gene into primary transcript mRNA (also known as pre-mRNA). This pre-mRNA usually still contains introns, regions that will not go on to code for the final amino acid sequence. These are removed in the process of RNA splicing, leaving only exons, regions that will encode the protein. This exon sequence constitutes mature mRNA. Mature mRNA is then read by the ribosome, and, utilising amino acids carried by transfer RNA (tRNA), the ribosome creates the protein. This process is known as translation. All of these processes form part of the central dogma of molecular biology, which describes the flow of genetic information in a biological system. As in DNA, ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a basic unit of heredity and the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and noncoding genes. During gene expression, the DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Transcription
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter DN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ligand
In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electron pairs, often through Lewis bases. The nature of metal–ligand bonding can range from covalent to ionic. Furthermore, the metal–ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic "ligands". Metals and metalloids are bound to ligands in almost all circumstances, although gaseous "naked" metal ions can be generated in a high vacuum. Ligands in a complex dictate the reactivity of the central atom, including ligand substitution rates, the reactivity of the ligands themselves, and redox. Ligand selection requires critical consideration in many practical areas, including bioinorganic and medicinal chemistry, homogeneous catalysis, and environment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinoic Acid Receptor Beta
Retinoic acid receptor beta (RAR-beta), also known as NR1B2 (nuclear receptor subfamily 1, group B, member 2) is a nuclear receptor that in humans is encoded by the ''RARB'' gene. Function This gene encodes retinoic acid receptor beta, a member of the thyroid-steroid hormone receptor superfamily of nuclear transcriptional regulators. This receptor localizes to the cytoplasm and to subnuclear compartments. It binds retinoic acid, the biologically active form of vitamin A which mediates cellular signalling in embryonic morphogenesis, cell growth and differentiation. It is thought that this protein limits growth of many cell types by regulating gene expression. The gene was first identified in a hepatocellular carcinoma where it flanks a hepatitis B virus integration site. A deregulation of this gene has also been detected in uterine cervical carcinoma preneoplastic lesions. The gene expresses at least two transcript variants; one additional transcript has been described, but its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corepressor (genetics)
In the field of molecular biology, a corepressor is a molecule that represses the expression of genes. In prokaryotes, corepressors are small molecules whereas in eukaryotes, corepressors are proteins. A corepressor does not directly bind to DNA, but instead indirectly regulates gene expression by binding to repressors. A corepressor downregulates (or represses) the expression of genes by binding to and activating a repressor transcription factor. The repressor in turn binds to a gene's operator sequence (segment of DNA to which a transcription factor binds to regulate gene expression), thereby blocking transcription of that gene. Function Prokaryotes In prokaryotes, the term corepressor is used to denote the activating ligand of a repressor protein. For example, the '' E. coli'' tryptophan repressor (TrpR) is only able to bind to DNA and repress transcription of the ''trp'' operon when its corepressor tryptophan is bound to it. TrpR in the absence of tryptophan is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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