p53 tumor suppressor vs Rb tumor suppressor
How to tell p53 tumor suppressor and Rb tumor suppressor apart when a board question makes them look alike.
p53: senses DNA damage and triggers G1 arrest or apoptosis; Rb: binds E2F to block the G1/S transition until it is phosphorylated.
Side by side
p53 responds to DNA damage by inducing p21 cell-cycle arrest, DNA repair, senescence, or apoptosis and is called the guardian of the genome.
Rb restrains the G1/S transition by binding E2F; phosphorylation by cyclin-CDK releases E2F and allows S-phase gene transcription.
TP53 loss removes damage-induced arrest and apoptosis, allowing genetically unstable cells to survive.
RB1 loss or excessive phosphorylation releases E2F constitutively, driving inappropriate S-phase entry.
Li-Fraumeni syndrome, many cancers, impaired apoptosis after DNA damage, and p21 failure support p53 loss.
Retinoblastoma, osteosarcoma risk, E2F dysregulation, and G1/S checkpoint release support Rb loss.
The trap
Both are tumor suppressors at G1/S, but p53 senses damage while Rb controls E2F entry into S phase.
Watch it explained
Test it nowThe repair move
For tumor suppressors, decide whether the stem tests damage response or E2F checkpoint braking.
Try a free question
CoreA 25-year-old woman with germline mutation in TP53 has a family history of osteosarcoma, breast cancer, brain tumors, leukemia, and adrenocortical carcinoma across multiple generations, with affected family members presenting in childhood and young adulthood. Which condition is most likely?
Show answer and explanation
Answer: A. Li-Fraumeni syndrome (germline TP53 mutation). Li-Fraumeni syndrome is germline TP53 mutation (autosomal dominant), causing predisposition to multiple cancers at young ages: sarcomas (osteosarcoma, soft tissue), breast cancer, brain tumors, leukemia, adrenocortical carcinoma. p53 is the 'guardian of the genome' at the G1/S checkpoint.
Why the other choices are tempting
- B. Familial retinoblastoma is germline RB1 mutation predominantly causing bilateral retinoblastoma in children plus osteosarcoma risk, not the broad Li-Fraumeni spectrum.
- C. BRCA1/2 mutations primarily cause breast and ovarian cancer, not the broad Li-Fraumeni spectrum with sarcoma and adrenocortical carcinoma.
- D. Lynch syndrome is DNA mismatch repair deficiency with colorectal, endometrial, and other cancers, not the Li-Fraumeni pattern.
- E. FAP is APC mutation with thousands of colonic polyps and certain colorectal cancer, not the Li-Fraumeni multi-tumor spectrum.
Flashcards
Tap a card to flip it.
What clue supports p53 tumor suppressor?
Choose p53 tumor suppressor when the stem gives this pattern: p53 responds to DNA damage by inducing p21 cell-cycle arrest, DNA repair, senescence, or apoptosis and is called the guardian of the genome.
What clue supports Rb tumor suppressor?
Choose Rb tumor suppressor when the stem gives this contrasting pattern: Rb restrains the G1/S transition by binding E2F; phosphorylation by cyclin-CDK releases E2F and allows S-phase gene transcription.
Quick answers
What is the fastest way to tell p53 tumor suppressor from Rb tumor suppressor?
p53: senses DNA damage and triggers G1 arrest or apoptosis; Rb: binds E2F to block the G1/S transition until it is phosphorylated.
What is the key clue for p53 tumor suppressor?
p53 responds to DNA damage by inducing p21 cell-cycle arrest, DNA repair, senescence, or apoptosis and is called the guardian of the genome.
What is the key clue for Rb tumor suppressor?
Rb restrains the G1/S transition by binding E2F; phosphorylation by cyclin-CDK releases E2F and allows S-phase gene transcription.
What is the common trap with p53 tumor suppressor vs Rb tumor suppressor?
Both are tumor suppressors at G1/S, but p53 senses damage while Rb controls E2F entry into S phase.