Regulation of Transcription-Factor Activity Flashcards
What are promoters? What is their function?
Direct binding of RNA polymerase ll to DNA, determine the site of transcription initiation, and influence the frequency of transcriptional initiation.
Describe promoter-proximal elements and enhancers.
Gene and cell-type-specific regulatory elements on DNA.
Describe transcription activators and repressors.
Modular proteins containing a single DNA-binding domain and one or more activation or repression domains.
Transcription factor activities can be _____ regulated by lipid hormones.
Directly
Some cells send signals to other cells by expressing and secreting a lipid soluble hormone. Lipid soluble hormones diffuse into the cell through the cell membrane and bind to a dedicated class of proteins called _________________?
Lipid-Hormone Receptors/Transcription Activators
Some receptors are located in the cytoplasm. Upon binding of the hormone the receptor/hormone complex moves to the _______. It is not a transcription factor- it binds to specific response elements (HRE) in target genes to regulate expression.
Nucleus
With other receptors that are already located in the nucleus, the binding of ____ changes their activity.
Hormones
Describe the steps associated with cell-surface receptors and intracellular signal transduction cascades.
- A cell sends a signal to other cells by expressing and secreting a lipid-soluble peptide hormone (ex. insulin).
- This peptide hormone reaches a membrane imbedded receptor on the surface of the recipient cell.
- The binding of the hormone initiates a signal transduction cascade (includes kinases that phosphorylate various proteins) through modifications of several proteins.
- Eventually, a transcription factor is activated by phosphorylation. It directs expression of its target gene.
Example: The glucocorticoid receptor (GR) translocates to the nucleus in the presence of _______.
Hormone.
When the hormone binds to the LBD (ligand binding domain), the _________ are excreted in the cytosol.
Chaperones
GFTs, co-activators, activators are all examples of transcriptional _________.
Activators.
Transcriptional activators regulate the release of the paused RNA pol ll by activating P-TEFb 1. _______ kinase, which phosphorylates and inactive factors .2 ______ that cause the pause.
- CDK9/CycT
- NELF, DSIF
RNA pol ll is loaded on the promoter and initiates transcription but pauses _____ of the promoter.
Downstream
Eukaryotic activators/repressors usually bind _________ to DNA elements in promoters or enhancers.
Directly
After the eukaryotic activator or repressor has bonded directly to the DNA elements in promoters or enhancers, they affect gene expression by recruiting multi-subunit ___________ that modulate chromatin structure or interact with RNA Pol ll and the GTFs.
Co-a avatar/co-repressor complexes
Activators/coactivators stimulate the assembly of
1. _________ and move nucleosomes 2. ______ from the promoters
- Preinitiation complexes
- Away
True or false? A cell needs to produce the specific set of activators required for a specific promoter/enhancer of a particular gene to express that gene.
True.
Repressors most frequently work through the build-up of _________ chromatin structures. Recall chromatin is DNA in eukaryotes packages with nucleosomes.
Repressive
Describe euchromatin.
De-condensed, lightly stained DNA is eukaryotes packaged with nucleosomes.
Describe heterochromatin.
Condensed, heavily stained, inaccessible to transcription factors DNA in eukaryotes packaged with nucleosomes.
Describe the role of chromatin in gene expression.
- Plays a central role in the selection of genes that will be expression any tissue or cell.
- Chromatin plays a role in the activation or repression of genes by DNA binding proteins.
Describe epigenetic regulation.
Transcription in eukaryotes takes place on the chromatin, that must be open for transcription to proceed. Chromatin-mediated regulation is an entirely new mechanism as compared to prokaryotes.
The nucleosome is built of 8 histones. Two of each: _____________.
H2A, H2B, H3, and H4.
The histones contain core domains that form the highly structured ___________.
Nucleosome
The histone N-termini are not structured and protrude away from the histone core. What are used to modify these N-termini?
Post-translational modifications (PMTs). The PMTs dictate the function of the DNA wrapped around the nucleosome.
The variety of PMTs (post-translational modifications) are referred to as “______”.
Histone codes.
