NAGE 3

Question 1

What direction does the RNA chain grow?

Answer 1

5’ to 3’ direction

Question 2

What is the antisense strand?

Answer 2

The DNA strand getting transcribed.

“Antisense” because opposite of the RNA getting produced

Question 3

Which enzymes carry out transcription?

Answer 3

RNA polymerases.

Question 4

What are the 3 types of RNA polymerase?

Answer 4

1. RNA Polymerase 1 - transcribes rRNA genes
2. RNA Polymerase 3 - transcribes tRNA and 5S RNA genes
3. RNA Polymerase 2 - transcribes genes encoding proteins into mRNA

Question 5

RNA synthesis has an elongation step. What step does it require to build a transcriptional complex?

Answer 5

Initiation step

Question 6

What is the gene promotor?

Answer 6

The DNA sequence at which the transcriptional complex assembles.

Question 7

What do transcriptional factors do?

Answer 7

Regulate the amount of gene transcription

Question 8

1. What do Transcriptional activators do?

2. What do Transcriptional repressors do?

Answer 8

1. Activate gene expression

2. Suppress gene expression

Question 9

What does the Basal Transcription Complex do?

Answer 9

Produces a low level of transcription, if other transcription factors are missing

It allows RNA Polymerase 2 to be phosphorylated and subsequently engage in transcription

Question 10

Explain how the Basal Transcription Complex works.

Answer 10

1. TF 2D binds to TATA. (TF 2D contains TATA Binding Protein (TBP) and TBP Accessory Factors (TAFs)).
2. Binding of TF 2D partially unwinds minor groove, and widens minor groove - allows extensive contact with bases.
3. Unwinding is asymmetrical with respect to TBP-TATA complex - ensures unidirectional transcription
4. TF 2A and TF 2B bind. TF 2B important as it can bind to TF 2D and RNA Polymerase 2.
5. RNA polymerase 2 has TF 2F attached. RNA polymerase 2 binds to TF 2B.
6. TF 2E//H/J binds to RNA Polymerase 2.
7. TF 2H promotes further unwinding of DNA.

Question 11

How do TFs work?

Answer 11

They bind onto TF binding sites and bend DNA. TFs interact with each other and basal transcription complex to regulate transcription.

Question 12

How do TFs facilitate transcription?

Answer 12

They help remodel chromatin.

Enzymatic Proteins are recruited that modify histones.

Causes nucleosome acetylation or deacetylation

Question 13

What does hyperacetylation do?

Answer 13

Stimulates gene expression

Question 14

What does hypoacetylation do?

Answer 14

Stimulates gene repression

Question 15

What are factors affecting TF expression?

Answer 15

1. Cell lineage
2. TF expression altered by extracellular signals (hormones/GFs/Mechanical Stress, etc)
3. Mutated TFs important in genetic disorders
4. Abnormal TF expression found in many human factors.