Transcriptional Circuits Flashcards
What is the rate of transcription of the transcriptome?
Only a fraction of the transcriptome is transcribed at any one given time
How do sigma factors in Prokaryotes mediate promoter recognition?
Sigma factors recognise the -10 and -35 motifs (highly conserved regions in prokaryotic promoters)
What is meant by an abundant transcript?
A gene expressed in every cell aka Housekeeping gene
e.g. Glycolytic enzymes genes
How are regulatory changes mediated?
Via regulatory transcription factors
Outline how the LAC Operon switch regulates transcription?
- LAC repressor binds upstream of of LAC Operon
2. prevents activation and transcription of LAC ZYA gene
What are the different levels a gene can be transcribed to?
- Abundant transcripts
- Rare transcript
- No transcript
Why are TFII and Sigma factors able to recruit RNA?
Occurs at every promoter due to genetics
What happens once the DNA is stably recruited to the Promoter?
RNA Pol. II is able to convert from a closed to an open complex
TATA box required to recruit TF
How is tissue specific transcription carried out in β-globin?
β globin promoter has ubiquitous factors in all cell types
has tissue specific TF GATA-1
only present in genes that are expressed in rbc
What do regulatory transcription factors do?
Dramatically alter RNA Pol.II recruitment and its ability to initiate transcription
In eukaryotes they influence local chromatin structure
Which transcriptional switches are present in eukaryotes?
- Oestrogen Responsive Transcription
- Tissue specific transcription (β globin)
- Complex regulatory Cycle (cell cycle)
What are rare transcript genes?
Genes that aren’t required as much and therefore are transcribed less
What is the LAC Operon?
Prokaryotic paradigm for the regulation of transcription
- required for transport and metabolism of lactose in E.Coli
What are Enhancers?
DNA sequences that enhance gene transcription by enhancing RNA Pol. recruitment to the promoter
How can tamoxifen be used to treat breast cancer?
Tamoxifen - competitive inhibitor of oestrogen
- binds to oestrogen receptor blocking transcription of genes prevalent in breast cancer
What is a transcriptome?
The segment of DNA that is Transcribed
What is required for LAC gene to be transcribed?
In order for gene transcription:
Sigma factor binding sequence and promoter region required
When CAP protein binds to complementary sequence transcription occurs
Where are enhancers found on the gene?
Enhancers can reside either 5’ or 3’ to a transcription unit can even be located on introns
Why are factors required for promoter recognition in both pro and eukaryotes?
Neither prokaryotes or eukaryotes RNA Pol. form stable contacts with DNA
- they just slide along the duplex without being able to efficiently recognise promoters
What other common regulatory transcription factors are present in eukaryotes?
- NF-Kb: triggered by immune stress
- CREB: triggered by Cyclic AMP
- Oestrogen receptor: triggered by Oestrogen
- ISGF3: triggered by Interferon
Explain what is meant by no transcript genes
Genes that are never transcribed in some cells
However can be expressed a lot in other tissues i.e. tissue specific
e.g. Globin
What are transcriptional switches?
Major biological regulatory mechanisms controlling the cell cycle and cell differentiation
What is the significance of the LAC ZYA gene?
Genes need to utilise lactose as a carbon source when glucose not present
- LAC transcribed (CAP binds)
What are inducible genes?
Genes that are transcribed via induction by certain stimuli
e.g. growth factors, viral infections, hormones etc.
