An insulator is a type of cis-regulatory element known as a long-range regulatory element. Found in multicellular eukaryotes and working over distances from the promoter element of the target gene, an insulator is typically 300 bp to 2000 bp in length. Insulators contain clustered binding sites for sequence specific DNA-binding proteins and mediate intra- and inter-chromosomal interactions.
Insulators function either as an enhancer-blocker or a barrier, or both. The mechanisms by which an insulator performs these two functions include loop formation and nucleosome modifications. There are many examples of insulators, including the CTCF insulator, the gypsy insulator, and the β-globin locus. The CTCF insulator is especially important in vertebrates, while the gypsy insulator is implicated in Drosophila. The β-globin locus was first studied in chicken and then in humans for its insulator activity, both of which utilize CTCF.
The genetic implications of insulators lie in their involvement in a mechanism of imprinting and their ability to regulate transcription. Mutations to insulators are linked to cancer as a result of cell cycle disregulation, tumourigenesis, and silencing of growth suppressors.
Insulators have two main functions:
Enhancer-blocking insulators prevent distal enhancers from acting on the promoter of neighbouring genes
Barrier insulators prevent silencing of euchromatin by the spread of neighbouring heterochromatin
While enhancer-blocking is classified as an inter-chromosomal interaction, acting as a barrier is classified as an intra-chromosomal interaction. The need for insulators arises where two adjacent genes on a chromosome have very different transcription patterns; it is critical that the inducing or repressing mechanisms of one do not interfere with the neighbouring gene. Insulators have also been found to cluster at the boundaries of topologically associating domains (TADs) and may have a role in partitioning the genome into "chromosome neighborhoods" - genomic regions within which regulation occurs.
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understand how the brain is organised and how function at multiple scales is
integrated to give rise to cognition and beh
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understand how the brain is organised and how function at multiple scales is
integrated to give rise to cognition and beh
A topologically associating domain (TAD) is a self-interacting genomic region, meaning that DNA sequences within a TAD physically interact with each other more frequently than with sequences outside the TAD. The median size of a TAD in mouse cells is 880 kb, and they have similar sizes in non-mammalian species. Boundaries at both side of these domains are conserved between different mammalian cell types and even across species and are highly enriched with CCCTC-binding factor (CTCF) and cohesin.
Cis-regulatory elements (CREs) or Cis''-regulatory modules (CRMs) are regions of non-coding DNA which regulate the transcription of neighboring genes. CREs are vital components of genetic regulatory networks, which in turn control morphogenesis, the development of anatomy, and other aspects of embryonic development, studied in evolutionary developmental biology. CREs are found in the vicinity of the genes that they regulate. CREs typically regulate gene transcription by binding to transcription factors.
La régulation de la transcription est la phase du contrôle de l'expression des gènes agissant au niveau de la transcription de l'ADN. Cette régulation modifiera la quantité d'ARN produit. Cette régulation est principalement effectuée par la modulation du taux de transcription par l'intervention de facteurs de transcription qui se classent en deux catégories : les éléments cis-regulateurs géniques, en coopération avec les facteurs transprotéiques. Il existe également des mécanismes de régulation de la terminaison de la transcription.
Plonge dans la neuroépigénétique, couvrant la structure de la chromatine, les modifications des histones, la méthylation de l'ADN et leur impact sur la transcription et l'hérédité des gènes.
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Temporal activation of Hox genes in mouse pseudo-embryos in vitro initiates at the anterior part of the cluster and is accompanied by asymmetric loading of cohesin. Posterior CTCF sites then successively act as transient insulators, regulating the timed tr ...