Oncogenes and Tumour Suppresors Flashcards
What are oncogenes?
Oncogenes are genes that can lead to tumour progression/cancer.
What does the EGFR/HER2 oncogene lead to?
Breast cancer if over-expressed.
What does the oncogene RAS lead to?
Many different cancers if over-activated.
What does the oncogene Cyclin D1 lead to?
Overexpression of this leads to about 50% of all breast cancer cases.
What does the oncogene C-Myc lead to?
Many different cancers if over-expressed.
What is Rb?
Retinoblastoma protein (Rb). It is a tumour suppressor and if it is missing or inactive, this can be identified in childhood by an eye tumour.
Where is Rb found?
In all nucleated cells.
How does Rb work?
It sequesters transcription factors, preventing the turning on of genes needed for the cell cycle to progress such as DNA polymerase or thymidine kinase.
How/why is Rb inactivated?
When the cell needs to enter the cell-cycle, Rb needs to stop sequestering the necessary transcription factors. Phosphorylation of the Rb unit by G1-CDKs or G/S-CDK complexes causes the release of the transcription factor.
What is E2F?
E2F genes code for a family transcription factors which regulate the expression of several genes needed for cell cycle progression.
What does p53 do?
P53 arrests cells in G1 with damaged DNA.
How is p53 activated?
Activation of protein kinases that phosphorylate p53, stabilize and activate it.
Why is p53 constantly being produced and degraded in the absence of DNA damage?
So that a cell can rapidly respond to any DNA damage.
How does p53 work?
Once p53 is activated, it becomes stable and active p53 can bind to the regulatory region of the p21 gene, leading to the transcription of the p21 mRNA.
What does p21 do?
It will sequester the G1/S-cdk and S-cdk complexes and in doing so prevent the progression of the cell cycle.
