L40 - Cell Reproduction: p53 Protein

overview

• ALL eukaryotes halt the cell cycle (reproduction) if DNA is damaged

p53 protein

→ animal cells use p53 to respond to DNA damage

• p53 is regulated at the level of protein stability → ITS NOT made, just ACTIVATED

  • activation of protein kinases phosphorylate p53 → stabilizing & activating it

  • if theres NO DNA damage : proteasome degrade p53

• p53 is a POSITIVE transcription factor → turns ON target genes

Roles of p53

with moderate DNA damage:

1. p53 halts cell cycle by turning on p21 gene → binds to regulatory (Cdk) proteins → inhibits Cdk

• can stop the cycle @ G1 or G2 check

2. p53 turns on DNA repair enzyme genes → fixes DNA damage

with severe DNA damage:

1. p53 causes apoptosis by turning on PUMA gene

• by p53 being activated by another phosphorus

KNOW diagram!!!

Examinable Content