Lecture 15a Flashcards
When is transcription above basal level?
When an enhancer is used.
When is transcription below basal level?
When a silencer is used.
T/F: When a silencer is used, RNA polymerase is not present.
False! RNA polymerase is present, however, initiation nor elongation cannot start.
What are 2 ways we can tell transcription is taking place in bacteria as opposed to in eukaryotes?
1) The mRNA is translated at the same time it is being transcribed.
2) The DNA that is being transcribed is stretched out and naked.
Where do transcription and translation occur in eukaryotes?
Transcription occurs in the nucleus.
Translation occurs in the cytoplasm.
What kind of proteins get transported into the nucleus?
Proteins with Nuclear Localization Sequences (NLSs) are transported into the nucleus.
What does importin do?
It is a protein that transports other proteins into the nuclear pores.
T/F: There is only one type of Nuclear Localization Sequence (NLSs).
False! There is a lot of diversity in NLSs.
What are steroid hormones?
They are produced by glands and secreted into the bloodstream, then taken up by cells.
What do steroid hormones bind?
Steroid receptors, which are transcription factors.
Generally speaking, what happens when a steroid receptor binds a steroid hormone?
This activates gene transcription/expression.
What type of hormone is glucocorticoid?
It is a steroid hormone.
What does glucocorticoid bind?
glucocorticoid binds a glucocortoid receptor.
When HSP90 is bound to the glucocorticoid receptor, is it active or inactive?
It is inactive.
When glucocorticoid binds the glucocorticoid receptor, what happens?
HSP90 is released.
When HSP90 is released, what is now exposed?
This exposes a nuclear localization sequence and a dimerization surface.
After the dimerization surface has been exposed on the glucocorticoid receptor, what occurs?
Two identical glucocorticoid receptors are able to dimerize to each other.
After the homodimer has formed, what occurs?
Importin will then bring it into the nucleus through the nuclear pores.
Generally speaking, what are Glucocorticoid Response Elements (GREs)?
They are enhancers.
Where are GREs located? What is the purpose of this location?
They are located near dozens of different genes.
The purpose of this is so that the hormone can activate many genes.
When the glucocorticoid dimer binds to the GRE, what happens?
Transcription of the target gene is activated.
T/F: Glucocorticoids are limited in what they do.
False! Glucocorticoids do a LOT of things depending on the cell type.
What are examples of what glucocorticoids do?
Fat breakdown, stimulate glucose synthesis, anti-inflammatory response, etc.
What is Chromatin?
This is the complex formed by the chromosomal DNA and the proteins that associate with the DNA across regions/domains of the chromosome.
