Transcription LO

Question 1

Describe chemical reaction of RNA pol

Answer 1

• forms phosphodiester bond between 3’ OH and 5’ phosphate of incoming nucleotide.
• OH group nucelophilic attack on phosphoanhydride bond linking alpha and beta phosphates of nucleotide
• results in new phosphodiester bond with 2 inorganic phosphates

Question 2

what direction does RNA grow in?

Answer 2

3’

Question 3

what are the 3 steps involved in transcription?

Answer 3

initiation
elongation
termination

Question 4

what are the 3 parts to initiation?

Answer 4

1. RNA pol binds to promoter sequence in dsDNA
2. Pol melts dsDNA near transcription start site to form transcription bubble
3. pol catalyzes reaction linking first 2 nucloside triphosphates together

Question 5

what is elongation in transcription?

Answer 5

movement of RNA pol down DNA catalyzing bonds and forming transcription bubble as it moves

Question 6

What is termination in transcription?

Answer 6

RNA pol releases completed RNA strand and dissociates from DNA

Question 7

what are the 4 RNA pol?

Answer 7

RNA pol I
RNA pol II
RNA pol III
Mitochondrial pol

Question 8

what does RNA pol I make?

Answer 8

rRNA (18S, 28S, 58S)

Question 9

What does RNA pol II make?

Answer 9

mRNA, snRNA,microRNA (regulates gene activity)

Question 10

What does RNA pol III make?

Answer 10

tRNA, 5S RNA (part of large ribosomal subunit), U6snRNA (involved in spliceosome), 7SK RNA (activates transcription)

Question 11

what does mitochondrial RNA make in relation to viral pol?

Answer 11

mitochondrial RNA

Question 12

what is a promoter?

Answer 12

region on DNA where transcription factors bind that are involved in transcription initiation

Question 13

What is the sequence of the TATA box?

Answer 13

5’ TATAAA 3’

Question 14

where is the TATA box located?

Answer 14

30 bp upstream of transcription initiation site

Question 15

what is the function of the TATA box?

Answer 15

determines transcription start site and directs binding on RNA pol II

Question 16

how does alpha-amanitin block transcription?

Answer 16

non-competitive inhibitor, binds allosterically to bridge helix (alpha helix between upper and lower jaws of RNA pol), blocks RNA chain elongation by preventing translocation of RNA

Question 17

how does rifampicin block transcription?

Answer 17

binds to beta subunit of bacterial RNA polymerase selectively. Blocks the RNA exit channel thus preventing elongation of mRNA

Question 18

what is Rifampicin used to treat?

Answer 18

broad spectrum for tuberculosis and leprosy

Question 19

what is the function of XPD and XPB?

Answer 19

DNA helicases used in transcription within TFIIH complex

Question 20

what is the function of CDK7?

Answer 20

kinase that phosphorylates C-terminal domain of RNA pol II which allows it to release from promoter

Question 21

what is the function of TFIIA?

Answer 21

stabilized binding of TATA box binding protein (TBP) to DNA

Does not specifically recognize DNA

Question 22

what is the function of TFIIB?

Answer 22

bridge between TFIID and RNA pol II

Question 23

what is the function of TFIID?

Answer 23

initially recognizes the promoter

Question 24

what is the function of TFIIE?

Answer 24

involved in DNA melting at the promoter

Question 25

what is the function of TFIIF?

Answer 25

assists in wrapping DNA around the pre-initiation complex (PIC)

Question 26

what is the pre-initiation complex (PIC)?

Answer 26

a group of general transcription factors that help bind RNA pol to the promoter and melt DNA

Question 27

what diseases do mutations in XPB, XPD, and p44 cause?

Answer 27

xeroderma pigmentosum, cockaynes syndrome, and trichothiodystrophy