Enhancer Deactivation
Enhancer Deactivation - Related Videos
01:25
Deactivation Processes: Jablonski Diagram
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2024
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
09:43
Reversible Cooling-induced Deactivations to Study Cortical Contributions to Obstacle Memory in the Walking Cat
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Cited by 3 •
2017
Complex locomotion in naturalistic environments requiring careful coordination of the limbs involves regions of the parietal cortex. The following protocol describes the use of reversible cooling-induced deactivation to demonstrate the role of parietal area 5 in memory-guided obstacle avoidance in the walking cat.
01:24
ortho–para-Directing Deactivators: Halogens
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2023
Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...
01:13
meta-Directing Deactivators: –NO2, –CN, –CHO, –CO2R, –COR, –CO2H
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2023
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for the...
03:00
Self-Evaluation: Self-Enhancement and Self-Verification
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2020
Social psychologists have documented that feeling good about ourselves and maintaining positive self-esteem is a powerful motivator of human behavior (Tavris & Aronson, 2008). In the United States, members of the predominant culture typically think very highly of themselves and view themselves as good people who are above average on many desirable traits (Ehrlinger, Gilovich, & Ross, 2005). Often, our behavior, attitudes, and beliefs are affected when we experience a threat to our...
FAQs
Several molecular changes can reduce enhancer output, and they do not act through a single route. Transcription factors may dissociate, lowering regulatory input; nucleosomes may reposition over the element or chromatin may compact, reducing accessibility; DNA methylation and repressive histone modifications can further reinforce a less active state. Distinguishing these mechanisms helps explain how activity is lost.
Accessibility determines whether regulatory proteins can reach the enhancer DNA. Nucleosome repositioning can place a nucleosome over the regulatory element, while compaction makes the surrounding chromatin less permissive. These structural changes provide a mechanism linking the physical organization of DNA to reduced transcription, even when the enhancer sequence itself has not been deleted.
During development, cells establish distinct and stable expression programs. Deactivating selected enhancers can help maintain those programs by reducing transcriptional input at particular regulatory elements. Studying this process therefore connects local changes in enhancer activity with broader questions of cell-state regulation, especially when investigators ask how gene expression remains controlled after developmental decisions are established.
Silencing and deletion perturb enhancer function in different ways. A silencing approach reduces activity while leaving the DNA element present, whereas deletion removes the enhancer sequence. Comparing these strategies can help separate effects of enhancer activity from effects associated with loss of the element itself, while also clarifying the relationship between an enhancer and its target promoter.
Experiments that silence or delete an enhancer can test whether changing that element alters transcription of a target gene. The resulting comparison helps investigators evaluate the functional connection between the enhancer and promoter rather than relying only on the enhancer’s sequence or location. Such studies can identify regulatory elements that make a meaningful contribution to gene control.
Regulatory disruption can contribute to disease, making enhancer activity relevant even when the altered region does not encode a protein. Genetic studies of deactivated or experimentally silenced enhancers can help identify noncoding regulatory elements with diagnostic or therapeutic relevance. These findings may support interpretation of disease-associated regulation by focusing attention on gene-control regions as well as coding sequences.