what are oncogenes and how do they affect the cell cycle
Oncogenes are mutated versions of normal genes (proto‑oncogenes) that make cells grow and divide too much, which can push the cell cycle into overdrive and lead to cancer. They do this by overstimulating “go” signals for cell division or blocking pathways that normally trigger cell death, so abnormal cells keep cycling instead of stopping.
Quick Scoop
Oncogenes act like a stuck accelerator in the cell cycle, while tumor suppressor genes are more like brakes. When the accelerator is jammed on and the brakes fail, cells can move through checkpoints in the cell cycle (G1, S, G2, M) with too few controls, increasing the chance of tumor formation.
What are oncogenes?
- Proto‑oncogenes are normal genes that promote healthy cell growth, division, and survival during development and tissue repair.
- When proto‑oncogenes are altered by mutation, overexpression, or chromosomal changes, they become oncogenes that can drive uncontrolled proliferation.
- Many oncogenes code for growth factors, receptors, signaling proteins, or transcription factors that sit in key regulatory pathways for the cell cycle.
How they affect the cell cycle
- Oncogenes can continuously send “proliferate” signals so a cell enters and passes the G1/S checkpoint even when external growth signals are absent.
- Some oncogenes make cyclins or cyclin‑dependent kinases (CDKs) overly active, shortening or bypassing normal control points in the cycle.
- Others, like bcl‑2 , tilt the balance away from apoptosis, allowing genetically damaged cells to survive and keep cycling instead of undergoing programmed cell death.
Oncogenes vs tumor suppressors
- Tumor suppressor genes normally slow the cell cycle, repair DNA, or trigger apoptosis, counterbalancing oncogene activity.
- Cancer often develops when oncogenes are overactive at the same time tumor suppressor pathways are lost or inactivated, removing both growth limits and quality control.
Common oncogene examples
- Receptor tyrosine kinases such as EGFR and HER2 amplify growth signals at the cell surface, driving repeated entry into the cell cycle.
- Intracellular signaling proteins like RAS and RAF keep downstream pathways (for example MAPK) “on,” promoting proliferation and reduced differentiation.
- Transcriptional co‑activators such as YAP can switch on sets of genes that favor cell cycle progression and tissue overgrowth.
In many modern cancer therapies, drugs are designed to specifically block oncogene‑encoded proteins, trying to “release” the stuck accelerator so the cell cycle can once again be controlled.
Information gathered from public forums or data available on the internet and portrayed here.