Effect Of Oestrogen On Gene Transcription Flashcards
What are the general principles involved in controlling the expression of a gene by controlling transcription?
> For transcription to begin the gene is switched on by specific transcription factors
> Each transcription factor has a site that binds to a specific base sequence of the DNA in the nucleus
> When it binds, it causes this region of the DNA to begin transcription
> mRNA is produced and the information it carries is then translated into a polypeptide
> When a gene is not expressed ( switched off ) , the site on the transcriptional factor that binds to DNA is inactive
> This means it cannot cause transcription and polypeptide synthesis
How does oestrogen stimulate the expression of a gene?
> Oestrogen is a lipid-soluble molecule and therefore diffuses easily through the phospholipid bilayer
> Once inside the cytoplasm, oestrogen binds with a site on a receptor molecule of the transcription factor
> The shape of this site and the shape of the oestrogen molecule are complementary
> This then changes the shape of the DNA binding site on the transcriptional factor, which can now bind to DNA (it is activated)
> The transcriptional factor can now enter the nucleus through a nuclear pore and bind to specific base sequences on DNA
> The combination of the transcriptional factor with DNA stimulates transcription of the gene that makes up the portion of DNA
