Transcription Regulation

What is an operon? (prokaryotes)

number of protein-producing genes may be linked together and controlled by a single promoter

What are constitutive genes?

expressed at essentially a constant level

Constitutive genes are also known as....?

"housekeeping"

Regulatory sequences of DNA are usually embedded in the ______ region of the genome?

noncoding

What are cis-acting transcription factors?

regulatory DNA sequences

What are trans-acting transcription factors?

regulatory molecules (bind to the DNA sequences)

Binding trans-acting factors to DNA is through....?

specific structural motifs (ex. zinc fingers)

Transcription factors modulate gene expression by...?

turning transcription on or off

What are the 2 categories of trancription factors?

1. general/basal

2. specific

What is the role of general/basal transcription factors?

- needed for priming transcription

- position & activate RNA polymerase II

What is the role of specific transcription factors?

- activate/repression of gene transcription

- important for tissue-specific gene expression

- cell growth & differentiation

How can the rate of transcription can be further increased?

binding of coactivators to enchancer regions

Enhancers contain ______ that bind (general/specific) transcription factors?

response elements

specific

What binds trans-acting proteins and regulate gene expression?

hormone response elements (HREs)

What superfamily functions as specific transcription factors?

Nuclear receptor (steroid hormones, vit D, retinoic acid, thyroid hormone receptors)

What is the hormone response system?

1. receptor-hormone complex enters the nucleus

2. dimerization

3. binds via a zinc finger motif to DNA at response element

4. recruitment of coactivators to the transcription activation domain

(+) GRE transactivation (increases/decreases) anti-inflammatory mediators?

increases

(-) GRE transactivation (increases/decreases) inflammatory mediators?

decrease

What is the role of corepressors?

inhibition of expression of certain genes

Insulin, epinephrine, and glucagon receptors are known as...?

cell-surface receptors

What is the pathway of cell-surface receptors?

1. binds with G-protein

2. production of adenylyl cyclase

3. rise in cAMP

4. activates protein kinase A

5. CREB protein is activated

6. start transcription

Iron is stored in ______?

ferritin

What protein binds to and transports iron in the bloodstream?

transferrin

When does transferrin receptor biosynthesis increase?

when available iron levels are low

Where is Apo B mRNA made where?

- liver (apo B-100)

- small intestine (apo B-48)

What happens during mRNA editing / posttranscriptional modification?

changing the sense/start codon to the nonsense/stop codon UAA

Stable mRNA (housekeeping) has a _____ half-life?

long half-life

Unstable mRNA (growth factors & gene regulatory proteins) has a ______ half-life?

short half-life

What is the signal for early degradation?

AUUUA