Regulation of Transcription-Factor Activity

Question 1

What are promoters? What is their function?

Answer 1

Direct binding of RNA polymerase ll to DNA, determine the site of transcription initiation, and influence the frequency of transcriptional initiation.

Question 2

Describe promoter-proximal elements and enhancers.

Answer 2

Gene and cell-type-specific regulatory elements on DNA.

Question 3

Describe transcription activators and repressors.

Answer 3

Modular proteins containing a single DNA-binding domain and one or more activation or repression domains.

Question 4

Transcription factor activities can be _____ regulated by lipid hormones.

Answer 4

Directly

Question 5

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 _________________?

Answer 5

Lipid-Hormone Receptors/Transcription Activators

Question 6

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.

Answer 6

Nucleus

Question 7

With other receptors that are already located in the nucleus, the binding of ____ changes their activity.

Answer 7

Hormones

Question 8

Describe the steps associated with cell-surface receptors and intracellular signal transduction cascades.

Answer 8

1. A cell sends a signal to other cells by expressing and secreting a lipid-soluble peptide hormone (ex. insulin).
2. This peptide hormone reaches a membrane imbedded receptor on the surface of the recipient cell.
3. The binding of the hormone initiates a signal transduction cascade (includes kinases that phosphorylate various proteins) through modifications of several proteins.
4. Eventually, a transcription factor is activated by phosphorylation. It directs expression of its target gene.

Question 9

Example: The glucocorticoid receptor (GR) translocates to the nucleus in the presence of _______.

Answer 9

Hormone.

Question 10

When the hormone binds to the LBD (ligand binding domain), the _________ are excreted in the cytosol.

Answer 10

Chaperones

Question 11

GFTs, co-activators, activators are all examples of transcriptional _________.

Answer 11

Activators.

Question 12

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.

Answer 12

1. CDK9/CycT
2. NELF, DSIF

Question 13

RNA pol ll is loaded on the promoter and initiates transcription but pauses _____ of the promoter.

Answer 13

Downstream

Question 14

Eukaryotic activators/repressors usually bind _________ to DNA elements in promoters or enhancers.

Answer 14

Directly

Question 15

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.

Answer 15

Co-a avatar/co-repressor complexes

Question 16

Activators/coactivators stimulate the assembly of
1. _________ and move nucleosomes 2. ______ from the promoters

Answer 16

1. Preinitiation complexes
2. Away

Question 17

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.

Answer 17

True.

Question 18

Repressors most frequently work through the build-up of _________ chromatin structures. Recall chromatin is DNA in eukaryotes packages with nucleosomes.

Answer 18

Repressive

Question 19

Describe euchromatin.

Answer 19

De-condensed, lightly stained DNA is eukaryotes packaged with nucleosomes.

Question 20

Describe heterochromatin.

Answer 20

Condensed, heavily stained, inaccessible to transcription factors DNA in eukaryotes packaged with nucleosomes.

Question 21

Describe the role of chromatin in gene expression.

Answer 21

1. Plays a central role in the selection of genes that will be expression any tissue or cell.
2. Chromatin plays a role in the activation or repression of genes by DNA binding proteins.

Question 22

Describe epigenetic regulation.

Answer 22

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.

Question 23

The nucleosome is built of 8 histones. Two of each: _____________.

Answer 23

H2A, H2B, H3, and H4.

Question 24

The histones contain core domains that form the highly structured ___________.

Answer 24

Nucleosome

Question 25

The histone N-termini are not structured and protrude away from the histone core. What are used to modify these N-termini?

Answer 25

Post-translational modifications (PMTs). The PMTs dictate the function of the DNA wrapped around the nucleosome.

Question 26

The variety of PMTs (post-translational modifications) are referred to as "______".

Answer 26

Histone codes.