Ninja Nerd cell cycle regulation video

Regulation of the Cell Cycle

Introduction to Cell Cycle Regulation
- Importance of understanding how cells progress and what prevents them from continuing throughout the cell cycle.
- Overview of cell cycle phases: G1, S, G2, and Mitosis (Prophase, Metaphase, Anaphase, Telophase).
- Concept of quiescent stage (G0) where some cells exit the cycle.

Interphase
- G1 Phase: Cell growth and preparation for DNA replication.
- S Phase: DNA synthesis and replication.
- G2 Phase: Preparation for mitosis.
Mitosis
- Prophase: Chromosomes condense, and the spindle apparatus begins to form.
- Metaphase: Chromosomes align at the metaphase plate.
- Anaphase: Sister chromatids are pulled apart to opposite poles.
- Telophase: Chromatids arrive at poles, and the nuclear envelope reforms.
- Cytokinesis: Division of the cytoplasm to form two daughter cells.

Key checkpoints ensuring proper cell cycle progression to prevent errors and mutations.
G1/S Checkpoint: Determines if the cell is ready to enter S phase.
G2/M Checkpoint: Checks for DNA replication errors before mitosis.
M Checkpoint (Metaphase to Anaphase): Ensures all chromosomes are lined up correctly before separation.

Proto-Oncogenes and Tumor Suppressor Genes
- Proto-oncogenes:
- Stimulate cell proliferation.
- Responsible for transitions between cell cycle phases.
- Tumor suppressor genes:
- Act as brakes on the cell cycle.
- Inhibit progression when conditions are not favorable (e.g., DNA damage).

Growth Factors: Chemicals that stimulate cell proliferation.
- Examples:
- Epidermal Growth Factor (EGF)
- Vascular Endothelial Growth Factor (VEGF)
- Platelet-Derived Growth Factor (PDGF)
- Mitogens: Alternate name for growth factors due to their role in triggering mitosis.
Receptors Responding to Growth Factors:
- G-protein coupled receptors (GPCRs): Activate intracellular signaling cascades.
- GQ Protein Pathway:
  - Activated by growth factor binding.
  - Converts Pip2 to DAG (diacylglycerol) and IP3 (inositol trisphosphate).
  - DAG activates Protein Kinase C (PKC), which activates transcription factors.
  - IP3 releases calcium, activating calcium-dependent kinases like Calmodulin.
- G-Stimulatory Protein Pathway:
- Engages adenylate cyclase, converting ATP to cAMP, activating Protein Kinase A (PKA).
Tyrosine Kinase Receptors:
- Require dimerization for activation, triggering phosphorylation of Tyrosine residues.
- Involves proteins like GRB-2 and RAS which activate MAP Kinase signaling pathway leading to transcription factor activation.
Janus Kinase (JAK) Receptors:
- Activation leads to signaling pathways that involve transcription activators (STAT).

Transcription Factors:
- Activated by signaling pathways and responsible for regulating genes that drive the cell cycle.
Cyclins and Cyclin-Dependent Kinases (CDKs):
- Cyclin D: Regulates G1 phase transition, associates with CDK4/6.
- Cyclin E: Mediates G1/S transition, associated with CDK2.
- Cyclin A: Functions in S and G2 phases, associates with CDK2.
- Cyclin B: Role in late G2 and M phase, associates with CDK1.

Retinoblastoma Protein (Rb):
- Binds to E2F transcription factor preventing cell cycle progression.
- Hyperphosphorylation by CDKs releases E2F to drive cell cycle.
p53 Protein:
- Guardian of the genome; manages repair pathways and apoptosis.
- Regulates DNA repair genes and responds to DNA damage signals.
- Influence of MDM2, an E3 ubiquitin ligase that inhibits p53 function.

ATM Gene:
- Monitor DNA integrity, alerts p53 to DNA damage.
- Initiates repair pathways or activates apoptosis if damage is extensive.
Apoptosis Induction:
- Involvement of BAX/BCL-2 interactions and downstream activation of caspases.

Importance of tight regulation of the cell cycle to prevent uncontrolled cell growth, mutations, and cancer.
- Review mechanisms for cell cycle regulation including checkpoints, growth factor signaling, and the roles of various genes and proteins.