M4 Lecture 2

Question 1

How many RNA polymerases do PROKARYOTIC cells have?

Answer 1

1, RNA pol I

Question 2

What are the subunits of RNA pol I in prokaryotes?

Answer 2

Sigma
2 Alpha
2 BETA, B, B’
omega

Question 3

Explain all the function of each subunit in RNA pol I in prokaryotes

Answer 3

Sigma = recognises promoter region in DNA,pribnow Box, initiates transcription
2 ALPHA= activates transcription
2 BETA = catalyse RNA nucleotides, ELONGATE RNA sequence, involved in termination
omega= assembling and folding in some genes

Question 4

How is RNA synthesis initiate in PROKARYOTES in terms of RNA polymerase I?

Answer 4

• Sigma subunit recognises promoter sequence which leads to RNA pol I binding, initiating transcription
• As RNA pol I moves into transcription region sigma subunit is removed
• aaBB’ catalyses RNA nucleotides elongating sequence

Question 5

What is RNA holoenzyme?

Answer 5

-comprises all RNA pol I Prokaryotic subunits
sigma,alpha,beta,omega

Question 6

What is the RNA prokaryotic core enzyme?

Answer 6

comprises unit alpha,beta,omega for POLYMERASATION
NO sigma

Question 7

What are the EUKARYOTIC RNA polymerases?

Answer 7

• RNA pol I
• RNA pol II
• RNA pol III

Question 8

What does each RNA pol in EUKARYOTES code for?

Answer 8

• RNA pol I = mRNA, rRNA
• RNA pol II = mRNA, sRNA
• RNA pol III = tRNA,sRNA,rRNA

Question 9

How do Eukaryotic RNA and prokaryotic RNA differ?

Answer 9

Eukaryotic RNA require transcriptional factor to start RNA synthesis whereas prokaryotic do NOT

Question 10

How is EUKARYOTIC RNA pol II recruited?

Answer 10

• TFIID, which is transcriptional factor made up of
• TBP = tata binding protein and
• TAF = tata binding protein associated factors
• TFIID binds to RNA pol II
• TBP bound recognises promoter sequence and leads to RNA pol II binding and hence initiates transcription

Question 11

How is RNA pol I EUKARYOTIC recruited?

Answer 11

• Promoter region contains UCE(upstream control elements) and core region
• UBF bind to both UCE and CORE region
• UBF loop DNA and bind to each other
• This creates space for SL1 binding factor
• SL1 = TPB + pol I TAF
• RNA pol is recruited to this complex, transcription is initiated

Question 12

How is RNA pol III recruited?

Answer 12

• tRNA gene contain particular promoter region
• Promoter region is bound by TFIIIC
• TFIIIB is recruited, which causes removal of TFIIIC
• This creates space for RNA pol III which binds to DNA, leading to RNA synthesis