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Related Concept Videos

General Transcription Factors01:30

General Transcription Factors

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Tissue-specific transcription factors contribute to diverse cellular functions in mammals. For example, the gene for beta globin, a major component of hemoglobin, is present in all cells of the body. However, it is only expressed in red blood cells because the transcription factors that can bind to the promoter sequences of the beta globin gene are only expressed in these cells. Tissue-specific transcription factors also ensure that mutations in these factors may impair only the function of...
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The TGF-β signaling pathway regulates cell growth, differentiation, adhesion, motility, and development. TGF-β ligands that induce TGF-β signaling are synthesized in their latent form. Several proteases or cell surface receptors such as integrins act upon the latent form, releasing the active ligand. There are three types of mammalian TGF-βs: (TGF-β1, TGF-β2, and TGF-β3) that bind as homodimers or heterodimers to TGF-β receptors. The TGF-β receptors...
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Gene transcription is regulated by the synergistic action of several proteins that form a complex at a gene regulatory site. This is observed in eukaryotes, where the regulation of gene expression is a complex process. Regulatory proteins in eukaryotes can broadly be classified into two types – regulators that bind directly to specific DNA sequences and co-regulators that associate with regulatory proteins but cannot directly bind to the DNA. These co-regulators are further divided into...
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Transcriptional regulators bind to specific cis-regulatory sequences in the DNA to regulate gene transcription. These cis-regulatory sequences are very short, usually less than ten nucleotide pairs in length. The short length means that there is a high probability of the exact same sequence randomly occurring throughout the genome.  Since regulators can also bind to groups of similar sequences, this further increases the chances of random binding. Transcriptional regulators form...
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Related Experiment Video

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A High Resolution Method to Monitor Phosphorylation-dependent Activation of IRF3
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PIC Activation through Functional Interplay between Mediator and TFIIH.

Sohail Malik1, Henrik Molina2, Zhu Xue1

  • 1Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.

Journal of Molecular Biology
|December 6, 2016
PubMed
Summary

The Mediator complex initially represses transcription by forming an inert preinitiation complex (PIC). TFIIH then uses ATP hydrolysis to activate the PIC, revealing Mediator

Keywords:
Mediator coactivator complexRNA polymerase IIpreinitiation complexpromoter meltingtriptolide

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Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Biochemistry

Background:

  • The Mediator complex is crucial for regulating gene transcription by influencing the preinitiation complex (PIC).
  • The precise role of Mediator in PIC formation and function, particularly after recruitment, remains incompletely understood.

Purpose of the Study:

  • To investigate the effects of the Mediator complex on basal transcription using an in vitro system.
  • To elucidate the functional interplay between Mediator and TFIIH during early PIC development.

Main Methods:

  • Reconstitution of an in vitro transcription system using purified components.
  • Gel mobility shift assays to analyze PIC formation.
  • Characterization of TFIIH with mutant subunits (XPB).

Main Results:

  • Mediator represses transcription under specific conditions, creating an inert PIC intermediate.
  • TFIIH, recruited by Mediator, relieves this repression via ATP hydrolysis.
  • This repression relief is linked to TFIIH's promoter melting activity.

Conclusions:

  • Mediator acts as an assembly factor, facilitating PIC maturation through multiple stages.
  • Initial Mediator engagement generates a transcriptionally inactive PIC intermediate.
  • Energy-dependent activation by TFIIH is required to complete PIC formation and initiate transcription.