transcription factors RNAi Flashcards
- What is a transcriptional factor in eukaryotes?
A molecule that moves from the cytoplasm of a cell to the nucleus, where it can bind to a specific base sequence on the DNA (promotor region) to stimulate transcription by stimulating the binding of RNA polymerase OR Binds to a specific base sequence called a repressor region and inhibit transcription. Transcription factors sometimes need to be activated by another molecule before they become activated.
- What is oestrogen?
A steroid hormone that can diffuse through the phospholipid bilayer. It activates a transcription factor that promotes the transcription of a proto-oncogene causing it to be permanently express and become an oncogene.
- How does oestrogen initiate transcription?
Oestrogen diffuses through the phospholipid bilayer into the cytoplasm of the cell. It binds to a receptor on a transcription factor form a complex. The DNA binding site of the transcriptional factor is changed when the oestrogen binds to the receptor, so it is now complimentary to a promoter region in the DNA. The transcriptional factor enters the nucleus through a nuclear pore, binds to the promoter region which stimulates RNA polymerase, and begins transcription of the gene.
- Why does oestrogen only affect target cells?
Only target cells have the oestrogen receptor on the transcription factor. Other cells do not.
- What is a promotor region?
A sequence of DNA that a transcriptional factor binds to, which stimulates RNA polymerase to begin transcription of the gene.
- What organisms can be affected by RNAi?
Eukaryotes and some prokaryotes.
- What is RNAi
RNA interference. It is the destruction of mRNA before it is translated into a protein.
- What carries out the process of RNAi
siRNA (small interfering RNA)
- Describe the structure of siRNA
A short single strand of RNA that is complimentary to mRNA from a target gene. It is bound to an enzyme that can hydrolyse mRNA into smaller sections.
- How does siRNA stop the production of polypeptides/proteins?
siRNA is complementary to the mRNA produced from the target gene. The RNAi binds to the mRNA and the enzyme cuts the mRNA (destroying it) preventing the translation of the protein, so the production of the protein is reduced.
- How can siRNA be used to treat disease?
They can be used to prevent translation of mRNA from genes that cause disease. For example if an oncogene is being expressed too much then the amount of protein produced can be reduced and therefore the rate of cell division reduced.
