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In transcription, a __________ binds to transcription factors and helps direct __________ to the promoter region.
What is a cis-acting element? Give an example of one.
- Specific sequences within DNA that exert an effect on the expression of a nearby gene.
- Enhancers are cis-acting elements.
What is a trans-acting element? Give an example of one.
- Regulatory proteins that bind to cis-acting elements effect expression of a gene.
- Transcription factors are trans-acting elements.
The metallothionein gene has several __________ or enhancers. It is constitutively expressed, but its expression can be induced by __________ or __________.
- cis-acting elements,
- heavy metals,
How does the metallothionein gene maintain basal expression levels?
- promoter sequences, along with their respective transcription factors.
How do glucocoricoids induce expression of the metallothioein gene?
The steroid receptor (GR) binds to the GRE.
Heavy metals induce metallothionein gene expression by __________ binding to the MRE (metal response elemnent).
How does TPA, a drug that actives PCK, induce expression of the metallothionein gene?
AP1 binds TRE (TPA response element)
Name 4 ways the activity of a transcription factor can be controlled.
- 1) Synthesis of the protein
- 2) Ligand binding
- 3) Phosphorylation/dephosphorylation
- 4) Binding/release of inhibitors that sequester the protein or affect its ability to bind DNA
B-catenin is regulated by its __________ and __________.
B-catenin regulation is part of which pathway?
Wnt signaling pathway
The Wnt signaling pathway controls many aspects of development including:
- Cell-cell interaction during embryogenesis,
- cell proliferation,
- cell differentiation
Name a few genes that are up-regulated by the Wnt signaling pathway.
Depending on __________, different genes can be up-regulated by the Wnt signaling pathway.
What happens to B-catenin in the absence of Wnt?
It gets degraded
In the absence of Wnt, B-catenin is bound by APC, axin, and which two other transcription factors? All four transcription factors are commonly called the __________.
- casein kinase1 (CK1)
- glycogen syntase kinase3 (GSK3),
- degradation complex
CK1 & GSK3 __________ B-catenin, which signals it to be __________ and degraded by the __________.
When B-catenin is degraded, what co-repressor binds to LEF1/TCF? What happens to transcription?
Groucho, it is suppressed
Wnt binds to what receptor and what co-receptor?
Frizzled and LRP
Upon Wnt binding to frizzled, __________ is recruited and actived. The __________ is then recruited.
- degradation complex
When recruited by the activated dishevelled, CK1 & GSK3 phosphorylate __________. As a result __________ is no longer phosphorylated and degraded.
What happens when B-catenin enters the nucleus?
- It binds LEF1/TCF,
- displacing Groucho,
- inducing transcription.
What are STATs and how are they acitivated?
- Signal Transducers and Activators of Trancription,
- by phoshorylation.
What is the overall function of STAT's?
They provide a direct link between signal transduction acriss the cell membrane and transcription.
In the absence of ligand, __________ STATs are found in the ________.
What phosphorylates STATs?
Janus kinases (JAKs)
What happens when STATs are phosporylated?
- They dimerize,
- enter the nucleus,
- bind response elements.
Binding of cytokine __________adjacent receptors, and JAKS cross-phosporylate each other on __________.
Activated JAKs, phosprylate __________ on tyrosines, causing STATs to dock on specific __________ on the receptor. JAKs then phosphorylate __________, causing them to dimerize and enter the nucleus.