Regulation of Transcription Initiation (9) Flashcards
Many activator proteins also bind to a …… which helps RNA polymerase bind to the promoter.
Meidator
What are cis regulatory elements?
DNA sequences forming part of a gene involved in its regulation
What may cis regulatory elements do?
1) Increase or decrease basal level expression
2) Specify responses to particular signals- response elements (are cis-regulatory elements)
An example of a cis regulatory element is..
The human metallothionein gene
What are the two functions of Metallothioneins
1) Bind toxic metal ions and so protect organisms from their effects
2) Store needed metal ions such as Zn2+
In humans transcription of the metallothieonein gene is induced by what?
Metal ions and glucocorticoid receptor; acting independently of each other.
What cis regulatory elements are involved in human metallothionein gene and its transcription?
.TATA .GC .BLE .TRE .E-box
What are the response elements involved in human metallothionein gene and its transcription?
MRE- responds to metals
GRE- responds to glucocorticoid
Each cis-regulatory element binds to activator proteins, what are the activator proteins for the human metallothionein gene?
AP2 binds to BLE
AP1 binds to TRE
SP1 binds to the GC box
MTF1 binds to MRE -when activated by binding Zn2+
Glucocorticoid receptor binds to GRE when activated by binding glucocorticoid hormone
What are the features of the B-globin gene?
.Multiple binding sites for GATA-1
.Cis-regulatory elements are far downstream of the gene
.Some GATA-1 binding sites overlap with binding sites of other regulatory elements.
What does the core promoter do?
Defines where RNA polymerase binds.
What is the proximal promoter?
A region near the core promoter
What are enhancers?
Cis-regulatory elements far from the core promoter
Cis-regulatory elements are recogniseable by there similarity to what sequence?
The consensus sequence
What are consensus sequences?
Consensus sequences are recognition sites for particular activator or repressor proteins that bind specifically to this sequence. More than one protein may bind to a single element, these proteins may alter chromatin structure or interact with the transcription complex to change binding of RNA polymerase to promoter.
A single type of cis-regulatory element can be found
1) In multiple copies in a single gene
2) In more than one gene
Transcription is regulated by
The combination of activator and repressor proteins that bind to cis-regulatory elements. Combinations of activator proteins can increase transcription as much as 10 fold.
Elements whose position is not critical are called what?
Enhancers
What hormones bind to receptors on the outside of the cell and exert their effect indirectly?
Peptide hormones
What is the most important second messenger for peptide hormones?
cyclic AMP
What is the principal glucocorticoid hormone?
Cortisol
Cortisol is released during….
Starvation or intense excersise
What are the physiological effects of cortisol?
- increases blood sugar
- Anti inflammatory and immunosuppressive action
Different naturally occurring mutations in the glucocorticoid receptor are associated with?
.Raised BMI
.Beneficial body composition in young adults and greater muscle strength in young men
In the liver cells cortisol INCREASES GLUCOSE PRODUCTION by what?
Gluconeogenesis from amino acids
Receptors for steriod hormones, thyroid hormones and retinoic acid constitute super family of what?
Ligand-responsive transcription factors
What do ligand responsive transcription factors do?
.bind to DNA
.interact with transcription complex to regulate transcription
.made up of domains with distinct functions
