#Question id: 4535
#Unit 3. Fundamental Processes
The activators bind—and the enhanceosome forms—in a highly cooperative manner, ensuring that all three activators must be present. The following are three ways the regulators might be binding cooperatively:
I- Through direct protein–protein interactions between them
II- By changes in the DNA caused by binding of one protein helping binding of another;
III- By the fact that the activators all interact simultaneously with the coactivator.
#Question id: 4536
#Unit 3. Fundamental Processes
The human b-interferon gene is activated in cells upon viral infection through some activators, EXCEPT one
#Question id: 4537
#Unit 3. Fundamental Processes
The enhancer DNA is __, but once the activators are bound it is relatively , HMGA1 the DNA and thus helps the final structure form.
#Question id: 4538
#Unit 3. Fundamental Processes
We first consider a generic case. Gene A is controlled by four signals (1, 2, 3, and 4), each working through a separate activator (activators 1, 2, 3, and 4). Gene B is controlled by three signals (3, 5, and 6), working through activators 3, 5, and 6. It shows-
#Question id: 4539
#Unit 3. Fundamental Processes
The yeast S. cerevisiae exists in three forms: two haploid cells of different mating types—a and alpha and the diploid formed when an a and an a cell mate and fuse. The a cell and the a cell each encodes cell-type-specific regulators: a cells make the regulatory protein a1, and alpha cells make the proteins alpha1 and alpha2. A fourth regulatory protein, called Mcm1, is also involved in regulating the mating-type-specific genes (and many other genes) and is present in both cell types which shows Combinatorial Control.
The arrangement of regulators at the promoters of a-specific genes and a-specific genes is
|
cell type: |
gene regulatory proteins: |
target genes: |
|
1.a cell (haploid) |
a1 Mcm1 |
aSG alphaSG |
|
2.αlpha cell (haploid) |
alpha 1 alpha 2 Mcm2 |
hSG |
|
3.a/αlpha cell (diploid) |
a1 Mcm2 alpha2 |
#Question id: 4540
#Unit 3. Fundamental Processes
Transcription of eukaryotic genes can be repressed in various ways. These include the four mechanisms
|
1. Competition |
a-Repression is caused by recruiting histone modifiers that alter nucleosomes in ways that inhibit transcript |
|
2. Inhibition |
b-A repressor binds to a site on DNA beside an activator and interacts with that activator, occluding its activating region |
|
3. Direct repression |
c-By binding to a site on DNA that overlaps the binding site of an activator, a repressor can inhibit binding of the activator to a gene and thus block activation of that gene. |
|
4. Indirect repression |
d-A repressor binds to a site upstream of a gene and, by interacting with the transcriptional machinery at the promoter in some specific way, inhibits transcription initiation. |