Nuclear Receptors Flashcards
Nuclear receptors are found?
inside the cell and are located both in the cytoplasm and the nucleus.
Ligands for nuclear receptor are typically __________ which enter the cell by diffusion through the cell membrane.
Hormones
When bound to hormones, nuclear receptors are able to bind ___________ ___________ in the nucleus .
Activator proteins.
Nuclear receptors bound to activator proteins then bind to ___________________________ where they promote___________ of genes through activation of RNA polymerase.
Hormone response elements , transcription
The net effect of activating nuclear proteins is increased synthesis of genes containing.
hormone response elements (HRE).
It is important to remember that the effect of gene synthesis is dependent on the role the resulting proteins plays in the cell
True or false
True
For example, activating one gene may promote cell growth while another may promote cell cycle arrest or apoptosis.
Some nuclear receptor ligands are involved in ______________ and _______________.
Cell growth and differentiation
These nuclear receptor ligands include ____________ _____________.
Steroid hormones.
Cell growth is regulated by controlling transcription of genes that promote cells to divide and/or differentiate.
True or false
True
Other nuclear receptor ligands, such as ___________ and _____________ control cell metabolism by promoting transcription of genes that regulate metabolic activity.
Glucocorticoids and thyroid hormones.
It is important to remember that the effect of a nuclear receptor is related to the __________ it activates and that there is a significant overlap between functions of different ___________________
Genes, hormone receptors
Example- glucocorticoids are involved in both regulate of metabolic activity and cell growth and cell death.
The term Orphan receptors generally refers to?
receptors where no endogenous ligand has been identified.
In the case of orphan nuclear receptor they do not appear to?
bind common hydrophobic molecules
In regards to orphan nuclear receptors. They may be involved in ___________ regulation or in activating protective measures in cells.
Metabolic
Their action is similar to other nuclear receptors except there is either_______________________________________.
no endogenous ligand or the ligand is unknown
What is the zinc fingers(DNA binding domain) in a nuclear receptor.
This region contains a “zinc finger” domain which is a specialized DNA binding structure in proteins that must access the base pairing in DNA in order to “read” the sequence
the zinc finger region enables the protein to
bind to specific DNA sequences
In nuclear receptors, there are two zinc finger domains linked by.
A hinge region
Flexing of the hinge plays a role in positioning the zinc fingers so that the receptor can bind the _____
HRE
The regulator domain is at the protein’s N-terminal end on the nuclear receptor and controls the activation of the________ and ______________.
receptor and its ability to bind and activate transcription
Within this region is the _____ domain that permits a low level of activation of the receptor even in the absence of _____
AT-1, ligand
The ligand binding domain binds _________, ____________ and ________ ________ of the receptors.
Agonists ,antagonists and inverse agonists
In the ligand binding domain Binding of ________ activates the receptor and enables it to bind activator and DNA thus initiating transcription activation. ____________ can prevent this process.
Agonists, Antagonists
Type 1 receptors are located outside the ________. They are bound to molecular chaperone proteins called ______________. On binding ligand, they dimerize and dissociate from the _____________. They then move into the nucleus where they bind _________ and ______ and activate transcription.
Nucleus, Heat Shock proteins, Heat shock proteins, heat shock proteins, activator and HREs
Type 2 receptors are _______, bound to ____________ in the _______.
Diners, repressor proteins nucleus
When ligands bind to type 2 receptor dimers, the _________ is released and a ____________ binds . This complex binds to the _______ and activates transcription. In the absence of ligand, the co-repressor prevents transcription.
Co-repressor, co-activator, HRE
Type 3 receptors are similar to type 1 but differ in the structure of the ____ they bind to.
HREs
Type 2 bind to inverted repeats or palindromic sequences while Type 1 receptors bind to direct repeats.
True or false
True
The difference between an inverted repeat and direct repeat is that the repeated sequence in an inverted repeats is the reverse compliment while a direct repeat is exactly the same as the first sequence.
True or False
True
The repeats may be at a large distance from one another or close together.
In regards to nuclear receptors.
Agonists: Activate the receptor and enable binding of ___________ proteins. Increase __________.
Co-activator, transcription
In regards to nuclear receptors Antagonists: Binding prevents activation of the receptor by preventing ___________ binding.
Co- activator
IN regards to nuclear receptors Inverse Agonists: Inverse agonists decrease the activity of a ________________when no agonist is bound. As mentioned in objective 5 above, the AT-1 region allows some activation of the receptor in the absence of the agonist. Inverse agonist block this activation
Nuclear receptor,
