L44: Cell proliferation checkpoints& cell death

• What is the role of the Rb protein in the cell cycle?

  It slows down entry into S phase.
• Why does the Rb protein slow down entry into S phase?

  To allow time for DNA repair in G1.
• What regulates the restriction point in the cell cycle?

  pRb protein regulates the restriction point.
• What happens when pRb is inactivated?

  It allows progression past the restriction point.
• What are the components of the G1 cyclin/CDK complexes?

  Cyclin D and CDK4/CDK6.
• What is the function of the G2/M checkpoint?

  It regulates entry into mitosis.
• What does the tumor suppressor protein p53 regulate?

  Both G1 and G2/M checkpoints.
• What does p53 do when DNA damage is detected?

  It stabilizes in the nucleus and activates genes.
• What is the consequence of losing p53 function?

  It creates genome instability.
• What is Li-Fraumeni syndrome associated with?

  Inheriting one functional TP53 gene copy.
• What triggers apoptosis according to the study material?

  DNA damage and other cellular stresses.
• What is the role of the HPV E6 protein?

  It inhibits p53 activity.
• What is the effect of the HPV E7 protein?

  It inhibits Rb protein activity.
• How do HeLa cells behave in the cell cycle?

  They accumulate mutations and have genome instability.
• What distinguishes apoptosis from necrosis?

  Apoptosis does not cause inflammation.
• What is the default state of cells regarding apoptosis?

  Apoptosis is the default state.
• What are the key features of apoptosis?

  • Cells shrink and condense
  • Nuclear fragmentation occurs
  • Apoptotic bodies are formed
  • Phagocytosis by other cells
  • No inflammation is stimulated
• What are the differences between apoptosis and necrosis?

  Apoptosis:

  • Orderly cell death
  • No inflammation
  • Intracellular contents retained

  
  

  Necrosis:

  • Uncontrolled cell death
  • Causes inflammation
  • Intracellular contents released
• What are the roles of CED-3 and CED-9 in C. elegans apoptosis?

  • CED-3: Required for cell death
  • CED-9: Suppresses apoptosis, promoting survival
• What are the main components of the cell cycle control system?

  • Cyclins
  • Cyclin-dependent kinases (CDKs)
  • Checkpoints (G1, G2/M)
  • Tumor suppressor proteins (p53, Rb)
• What is the significance of Caenorhabditis elegans in apoptosis research?

  • Key insights into genetic regulation
  • Model organism for studying programmed cell death
  • Nobel Prize awarded for discoveries
• What are the consequences of TP53 mutations?

  • Reduced tumor suppression
  • Associated with ~50% of human cancers
  • Increased risk of early adulthood tumors
• What triggers the stabilization of p53 in the nucleus?

  • Detection of DNA damage
  • Activation of stress response pathways
• What is the role of caspases in apoptosis?

  • Cleave proteins leading to cell death
  • Activated by loss of trophic signals
• What is the default state of apoptosis?

  Apoptosis is our DEFAULT state
• What is required to stop apoptosis?

  Continual survival (trophic) signals
• What are the internal triggers for apoptosis?

  Recognition of irreparable DNA damage
• What can cause DNA damage leading to apoptosis?

  Radiation, chemotherapy, replication mistakes
• What are external triggers for apoptosis?

  Heat, radiation, starvation, hypoxia
• How does the immune system trigger apoptosis?

  By recognizing virally-infected cells
• What is the consequence of a virus mutating to avoid detection?

  It can trigger an arms race
• What role does apoptosis play in fetal development?

  It removes webbing between fingers
• Who won the Nobel Prize in 1999 and for what discovery?

  Günter Blobel for protein transport signals
• What did Jim Rothman, Randy Schekman, and Thomas Südhof discover?

  Machinery regulating vesicle traffic
• What did Leland Hartwell, Tim Hunt, and Sir Paul Nurse discover?

  Key regulators of the cell cycle
• What did Sydney Brenner, H. Robert Horvitz, and John E. Sulston discover?

  Genetic regulation of organ development
• What is the issue with inclusivity in Nobel Prizes?

  Over 75% awarded to Western Europe and America
• Who was the first woman to win a Nobel Prize?

  Gerti Cori in 1947
• What is the consequence of the cell cycle running at full speed?

  Increased risk of DNA errors
• Why are brakes needed in the cell cycle?

  To provide time for DNA repair