NAGE 3 - Gene Organisation & Transcription Flashcards
List the stages of transcription
1) DNA strands unwind
2) Antisense strand is used as a template for replication, with ribonucleotides pairing with the exposed DNA bases
3) RNA polymerase 2 joins the ribonucleotides in the 5’ to 3’ direction
What are the functions of the 3 different RNA polymerases?
RNA polymerase I - Transcribes rRNA genes
RNA polymerase II - Transcribes genes encoding proteins to mRNA
RNA polymerase III - Transcribes tRNA and 5s RNA genes
What are the two main componants of a gene promotor region?
There is a transcription factor binding site, and a TATA region where the initiation complex forms.
What are the stages of formation of the basal transcription complex?
1) TF II D binds to the TATA sequence, as it contains TATA binding protein. The TF II D unwinds the DNA helix, widening the minor groove and ensuring it is asymmetric.
2) TFIIA and TFIIB then bind to the TFIID.
3) RNA polymerase binds to TFIIB, also bound to TFIIF.
4) TFIIE, TFIIH and TFIIJ also bind to RNA polymerase
Which transcription factor promotes further unwinding of the DNA helix to facilitate RNA synthesis?
TFIIH
Why is the basal transcription complex important?
It allows RNA polymerase to be phosphorylated, resulting in a low level of transcription.
How do transcription factors bind to the promotor region?
They bend the DNA on binding, interacting with each other to modulate transcription.
How do transcription factors act as activators or suppressors?
At the nucleosome stage of DNA packing, transcription factors modify histones via enzyme activity by the addition or removal of acetyl groups.
How does hypoacylation affect gene expression?
Gene expression will decrease
How does hyperacylation affect gene expression?
Gene expression will increase.
How is transcription factor expression determined?
It is determined by cell lineage and also by signlas external to the cell (such as hormones, growth factors, mechanical stress, heat, cell contact, light, touch)
How do transcription factors affect inflammation?
Transcription factors are involved in the production of cytokines, which increase inflammation. An example of a transcription factor involved is NFkB
How does aspirin reduce inflammation?
Aspirin inhibits the breakdown of an inhibitor of NFkB (IkB). This means NFkB will remain in the cytoplasm, and transcription of cytokine genes cannot occur.
How are transcription factors involved in leukaemia?
Half of acute lymphoblastic leukaemias are due to mutated transcription factors. Mutations are generally caused by chromosomal translocations.
How is the oestrogen receptor involved in breast cancer?
The oestrogen receptor is a transcription factor.over half of breast cancers are due to overexpression of the oestrogen receptor.
