What direction does the RNA chain grow?
5’ to 3’ direction
What is the antisense strand?
The DNA strand getting transcribed.
“Antisense” because opposite of the RNA getting produced
Which enzymes carry out transcription?
RNA polymerases.
What are the 3 types of RNA polymerase?
- RNA Polymerase 1 - transcribes rRNA genes
- RNA Polymerase 3 - transcribes tRNA and 5S RNA genes
- RNA Polymerase 2 - transcribes genes encoding proteins into mRNA
RNA synthesis has an elongation step. What step does it require to build a transcriptional complex?
Initiation step
What is the gene promotor?
The DNA sequence at which the transcriptional complex assembles.
What do transcriptional factors do?
Regulate the amount of gene transcription
- What do Transcriptional activators do?
2. What do Transcriptional repressors do?
- Activate gene expression
2. Suppress gene expression
What does the Basal Transcription Complex do?
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
Explain how the Basal Transcription Complex works.
- TF 2D binds to TATA. (TF 2D contains TATA Binding Protein (TBP) and TBP Accessory Factors (TAFs)).
- Binding of TF 2D partially unwinds minor groove, and widens minor groove - allows extensive contact with bases.
- Unwinding is asymmetrical with respect to TBP-TATA complex - ensures unidirectional transcription
- TF 2A and TF 2B bind. TF 2B important as it can bind to TF 2D and RNA Polymerase 2.
- RNA polymerase 2 has TF 2F attached. RNA polymerase 2 binds to TF 2B.
- TF 2E//H/J binds to RNA Polymerase 2.
- TF 2H promotes further unwinding of DNA.
How do TFs work?
They bind onto TF binding sites and bend DNA. TFs interact with each other and basal transcription complex to regulate transcription.
How do TFs facilitate transcription?
They help remodel chromatin.
Enzymatic Proteins are recruited that modify histones.
Causes nucleosome acetylation or deacetylation
What does hyperacetylation do?
Stimulates gene expression
What does hypoacetylation do?
Stimulates gene repression
What are factors affecting TF expression?
- Cell lineage
- TF expression altered by extracellular signals (hormones/GFs/Mechanical Stress, etc)
- Mutated TFs important in genetic disorders
- Abnormal TF expression found in many human factors.
