Transcription factors Flashcards
Promoter
DNA base sequence before a gene that regulates whether the following gene is transcribed or not thus will translate for a polypeptide or not
Are promoter base sequence transcribed?
No
Where is the promoter located on a gene?
‘upstream’ of where the gene is
AKA appears before the gene in the direction of RNA polymerase works
What binds to promoter to regulate transcription of the gene?
Transcription factor
Can transcription factors inhibit or stimulate transcription when binding to a promoter of a gene?
Can do both
Where do transcription factors move to?
Are in the cytoplasm but diffuse into nucleus to chromosomes to promoter for specific gene in a chromosome
Example of transcription factor to learn?
Oestrogen as a steroid hormone can release a transcriptional factor and can target specific promoters for inhibition/stimulation of specific target genes
Why can oestrogen enter the cell from the blood?
Is non polar so can directly enter cell by simple diffusion over non polar phospholipid bilayer
What does oestrogen do when it enters a cell?
Binds to a receptor on the transcriptional factor inside the nucleus
Where does oestrogen bind to on a transcription factor?
Receptor
What happens when oestrogen binds to receptor on transcription factor?
The transcription factor changes shape: tertiary structure changes so DNA binding site is now complementary to promoter base sequence of the target gene
Why can transcription factor bind to promoter of the target gene?
Because transcription factors dna binding site changed tertiary structure to be complementary to specific promoter for this target gene
When transcription factor (with oestrogen) binds to promoter………..
Activates RNA polymerase to transcribe the target gene
Can oestrogen effect any cell?
No Oestrogen will only have an effect on cells that contain transcription factors with an oestrogen receptor
Because only then will the transcription factor change tertiary structure to bind to complementary promoter for a target gene
What does oestrogen + its transcription factors usually trigger?
Activation of RNA polymerase to transcribe genes related to female puberty eg breast development
Drugs similar in shape to oestrogen can….
Bind to transcription factor’s binding site for oestrogen
Prevents oestrogen binding so therefore no change in tertiary structure so no activation of RNA polymerase for transcription of this gene
Inhibits female breast development as a result
How do transcription factors reprogram donor cells to iPS cells?
Bind to complementary promoter and inhibits transctription of specific genes
So cell is no longer specialised because certain polypeptides not translated (phenotype not expressed) = stem cell
