MBG 3040 Molecular Biology of the Gene
- F21 with Dr. Karunagoda Midterm exam
prep Solution University of Guelph
How many eukaryotic RNA polymerases are there? What are they called? - answer is 3- RNA
polymerase I, II, and III
Where does transcription and pre-mRNA processing occur? - answer is Nucleus
Where does translation and protein modification occur? - answer is Cytoplasm
Where is RNA Pol I found and what is its main function? - answer is - nucleolus (suggests txn of
rRNA genes)
- accounts for most cellular RNA synthesis
Where are RNA Pol II and III found? - answer is Nucleoplasm
Which RNA polymerase has the least RNA synthesis activity? - answer is RNA Pol II
What is the highly toxic substance found in poisonous mushrooms (genus Amanita)? - answer
is α-amanitin
What is the effect of α-amanitin at low concentrations? High? - answer is Low: inhibits Pol II
completely, no effect on Pol I and III
,1000-fold higher: inhibits pol III in most eukaryotes
What does RNA Pol I make the precursors to? - answer is 28S, 18S and 5.8S rRNAs
What does RNA Pol II make the precursors to? - answer is mRNAs, snRNAs, miRNAs
What does RNA Pol III make the precursors to? - answer is tRNAs, 5S rRNA, other small RNAs
What is the significance of 7SL RNA? - answer is Component of the signal recognition particle
(SRP) universally required for co-translational protein targeting
What is the significance of 7SK RNA? - answer is Plays role in regulating transcription by
controlling the positive transcription elongation factor P-TEFb
What does P-TEFb stand for and what does it do? - answer is - positive transcription elongation
factor
- multiprotein complex that plays essential role in regulation of txn by RNA Pol II in eukaryotes
What is hnRNA and what polymerase produces it? - answer is - ill-defined class of RNA
produced by RNA Pol II
- most hnRNAs are precursors of mRNA (pre-mRNA)
What do small nuclear RNAs do? - answer is snRNAs participate in the maturation of hnRNAs to
mRNAs
,What do microRNAs do? - answer is miRNAs control expression of many genes by causing
degradation of, or limiting the translation of their mRNAs
How many subunits do the three RNA Pol have? What are the common ones? - answer is - ~12
subunits each
- 5 common subunits: RPB5, 6, 8, 10, and 12
What are the functions of the subunits that are common to all 3 yeast RNA polymerases? -
answer is - Rpb5, Rpb6, Rpb8, Rpb10, Rpb12
- little is known about their function
- found in all 3 polymerases suggests they play roles fundamental to the transcription process
What is special about the phosphorylation of Rpb1, Rpb2, and Rpb6? - answer is - Rpb1/6 are
heavily phosphorylated
- Rpb2 is lightly phosphorylated
Which subunits of RNA polymerase II are essential for enzyme activity in yeast? - answer is The
three largest ones: Rpb1, Rpb2, Rpb3
Describe the general structure of RNA polymerases 1, 2, and 3. - answer is - complex structure
- 2 large subunits (>100 kDa)
- variety of smaller subunits
- resembles the prokaryotic core polymerases
Describe the structure of prokaryotic core polymerases. - answer is - 2 high molecular mass
subunits (β and β')
, - 3 low molecular mass subunits (2 α and an ω)
How do Rpb1, 2, and 3 (yeast) compare to the core subunits of bacterial RNA polymerases (E.
coli)? - answer is - Rpb1 binds DNA (so does E. coli β')
- Rpb2 is at/near the active RNA pol II site, involved in transcription start site selection and
elongation rate (so is E. coli β subunit)
- Rbp3 and E. coli α are homologous (unknown function)
What special feature does RNA pol II Rpb1 subunit have? What is it's significance? - answer is -
carboxy-terminal domain (CTD) consisting of a 7 AA repeat (YSPTSPS)
- 26 repeats in yeast, 52 in mammals
- removal of >50% of the repeat is lethal
- regulated by proteolysis and phosphorylation
- involved in initiation, elongation, mRNA processing, and mRNA export to cytoplasm
What is the role of a proximal promoter (Class II Classical Promoters)? - answer is - helps
attract general transcription factors and RNA polymerase
includes promoter elements upstream of the transcription start site
What are the two parts of a Class II Classical Promoter? - answer is Core promoter and
proximal promoter
Describe the core promoter of a class II Classical promoter. - answer is - shortest sequence
(~40bp) at which an RNA pol can initiate txn
- contains up to 6 conserved elements (at least one is missing in most promoters): BRE, TATA
box, Inr, DCE, MTE, and DPE
- attracts GTFs and Pol II at the basal level, sets txn start site and direction of txn
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