Transcriptional Circuits In Prokaryotes And Eukaryotes Flashcards
What is a transcriptome?
The segment of the genome that is transcribed
How much of the transcriptome is transcribed at one time?
A fraction
What are the three levels genes can be transcribed at?
1 (abundant)
2 (rare)
3(no transcription)
Inducible genes
Genes that aren’t expressed or are hardly expressed at all react to a stimuli and are them transcribed abundantly
What is recognition of promoters mediated by?
Initiation factors
What are the initiation factors in prokaryotes and eukaryotes
Sigma factor (prokaryotes) TF11 basal transcription machinery (eukaryotes)
Once stably recruited to DNA, what is able to convert DNA from a closed to an open complex
RNA polymerase
What’s a consensus sequence?
A sequence you are most likely to find if you were working on a base sequence
What do sigma factors recognise that enables RNA promoters to make stable contacts with DNA
-35 and -10 motifs
What is the sigma factor in eukaryotes
TATA box binding factor (TBP)
Why is a TATA box needed?
Needed to recruit general transcription factors and then RNA polymerase
What are regulatory transcription factors?
They mediate regulatory charges
What do regulatory transcription factors do in both prokaryotes and eukaryotes?
They function to dramatically alter the level of recruitment of RNA polymerase and/or its ability to initiate transcription
What can regulatory transcription factors do only in eukaryotes?
They can influence local chromatin
What is the lac operon
A prokaryotic paradigm for the regulation of transcription
Do regulatory transcription factors have to unwind the DNA double helix to see their target?
No, so an intact DNA molecule can present info to the cell
What is the transcriptional switch in prokaryotic cells?
The lac operon
What are the transcriptional switches in eukaryotic cells?
Oestrogen-responsive transcription
Tissue specific transcription (beta globin)
A complex regulatory circuit (cell cycle)
What do bacteria prefer to use as an energy source rather than lactose and why?
Glucose as it provides more energy for ATP
How is the lac gene switched off in bacteria if glucose is present?
The CAP protein is only active under low glucose conc. if there is no lactose present, the lac repressor binds to the DNA in the promoter region
What is the transcription factor if immune stress is the trigger?
NF-KB
What is the transcription factor if cyclic AMP is the trigger?
CREB
What is the transcription factor if oestrogen is the trigger?
Oestrogen receptor
What is the transcription factor if interferon is the trigger?
ISGF3
Give the steps for steroid hormone signalling
Steroid ->receptor protein -> hormone -> receptor complex -> transcription/mRNA -> New protein
Give one way therapeutic drugs can be targeted
Interfering with the interactions between regulatory and general transcription factors
What is tamoxifen and what is it used for?
A competitive inhibitor for oestrogen so it means that the oestrogen-responsive translation can’t take place. Used as a cancer treatment
How does tissue-specific transcription (beta globin) take place?
As the cell differentiates, the ubiquitous factors start expressing their gene and over time, the tissue-specific factor becomes more common
How is the cell cycle regulated?
The promoters for G1s transition genes are activated by a factor called E2F
Give the steps of cell cycle regulation
E2F activity is repressed in G0 and early G1 by the product of the retinoblastoma gene (pRB).
If the pRB is phosphorylated, then it can no longer bind to the E2F and it can then translate the gene.
