Chapter 36 - Transcription Flashcards
What does the promoter do?
It is where the RNA polymerase binds to to ensure the right start site
binds 30 nucleotides upstream of the start site
Differentiate cis-acting factor from trans-acting factor
Cis-acting = regulates nearby gene expression
Trans- acting = proteins that bind to cis factors and regulate that gene mismo
Promoter for prokaryotes?
TATAAT box or Pribnow box
Promoter for eukaryotic DNA
TATA box or Higness box
DNA sequences that accelerates trasncription
Enhancers
DNA sequences that inhibit transcription
Silencers
Where is the mRNA found? What is its function?
primarily in the nucleus then goes out to cytoplasm
copies the information from the DNA template strand
What does the sigma factor do?
The sigma factor finds the promoter via high affinity base pair
Only found in prokaryotes
What is the function of 7-methylguanosine triphosphate caps?
They are needed for the processing of mature mRNA and to prevent exonucleolytic attack
RNA Polymerase that synthesizes rRNA
RNAP I
RNA Polymerase that synthesizes mRNA, miRNA, SnRNA?
RNAP II
What toxin is RNAP II sensitive to?
alpha-amanitin toxin
RNA Polymerase that synthesizes tRNA and microRNA?
RNAP III
What does (+1) mean?
start of transcription site
5’ terminal of mRNA
beyond is downstream
What does (-1) mean?
It marks the promoter region
proceeds away from the initiation site (upstream)
termination protein for prokaryotes? Describe it?
Rho factor - ATP-dependent RNA stimulated helicase that disrupts RNA-DNA complex
if a gene does not have a TATA box then how is the promoter region known?
By the frequency of GC/CAAT boxes
If the eukaryotes do not have sigma factor then how is the RNAP guided to promoter region?
Via trans-acting element: General Transcription Factors (GTFs)
component of TFIID?
TATA binding proteins + 14 TAFs
What is the function of TFIIF?
equivalent od bacterial sigma factor
tethers RNAP to correct start site
What is the function of TFIIH?
It has a:
Helicase - causes local unwinding
Kinase - phosphorylases RNAP, allowing clreaing of promoter
What is the function of TFIID?
Binds to the TATA box promoter element
When is RNA Polymerase II activated?
When Ser and Thr of Carboxyl Terminal Repeat Domain (CTD) are phosphorylated
How to access promoter sequence wrapped in nucleosomes?
transcription factors bind to DNA then recruits chromatin remodelling and modefying coregulatory factors
Differentiate Stepwise Assembly from Recruitment Hypothesis
Stepwise Assembly - transcription activators function by stimulating PIC formation or as bridging factor to create PIC (one by one they bind to promoter
Recruitment Hypothesis - states that activators and coactivatorsss function to recruit a preformed holoenzyme-GTF complex to the promoter (meaning buo na siya bago magbind sa promoter)
What does polycistronic mean?
In bacteria, proteins are synthesized in just one strand
Promoters with both TATA and Inr (Initiation Sequence) are more actively transcribed. True or False?
True
Differentiate Rho-factor independent from Rho-factor dependent
Rho-factor Independent - binds to G-C rich region, allows formation of a self-complimentary hairpin loop that contains UUUUs after it
Rho-factor dependent - binds to C rich region containing an ATP-dependent Helicase that separates DNA from RNA
What is the probable termination sequence in eukaryotes
AAUAAA
Least tightly bound histones
H1
Action of Actinomycin D
lodges between G-C pairs and effectively stops transcription
What is the action of Rifampacin?
binds to beta subunit of RNAP inhibiting formation of initiation complex
What is the action of Quinolones?
Inhibits DNA gyrase (stops replication and transcription)
