The document discusses the cell cycle and its regulation. It begins by outlining the four main phases: G1, S, G2, and M. Checkpoints exist to monitor DNA damage and proper chromosome attachment before transitions. Research led to the discovery of cyclins and cyclin-dependent kinases (CDKs) that control cell cycle progression. Specifically, maturation promoting factor (MPF), composed of cyclin B and CDK1, induces mitosis. Protein destruction via the anaphase promoting complex (APC) also regulates the cell cycle. Growth and DNA integrity checkpoints in G1 determine whether a cell divides.

1. Advanced Cell Biology
2014 1nd Semester
Department of Animal Science
Chungbuk National University
8th Lecture

2. 1st week : Introduction
3rd week :Research Strategies For Cell Biology
5nd week : Nucleus, Transcription and Splicing
7nd week : Membrane and Channel
9nd week : Membrane Trafficking
11nd week : Cell Signaling
13nd week : Cytoskeleton
15nd week : Cell Cycle

3. Cell Cycle

5. G1: originally described as a gap between mitosis and DNA replication;
now appreciated to be the time when cells grow and check for DNA damage
and sample the environment to make the pivotal decision to replicate their
genomes and progress through the cell cycle.
S: phase when the genome is replicated.
G2: originally described as a gap between DNA replication and mitosis; now
appreciated to be the time when cells check for completion of DNA replication
before entering mitosis.
M: Mitosis and cytokinesis separate the replicated genome into two daughter
cells.
G0: Most differentiated cells in higher eukaryotes withdraw from the cell cycle
into this stage.

6. G1 restriction point: Monitors cell size, environmental
conditions, and interactions with neighbors and matrix.
G1/S DNA damage checkpoint: Stops the cell cycle if DNA
damage is detected.
G2/M DNA damage checkpoint: A protein kinase cascade
stops the cell cycle until all DNA is replicated.
Metaphase spindle assembly checkpoint: Delays
separation of daughter chromatids until all are attached to the
mitotic spindle.
Checkpoints control transitions
between the cell cycle phases

7. Cyclin and Cyclin Dependent Protein Kinase

8. Discovery of Cyclin and Regulators
- Temperature Sensitive Yeast mutant defective in Cell Cycle
- Isolations of cdc mutants

10. Xenopus embryo as model system for
Cell Cycle Research

11. Xenopus egg extract as in vitro model for
Cell Cycle Research

12. Maturation Promoting Factor (MPF)
Some protein(?) factors inducing Nuclear Membrane Breakdown and spindle Formation

14. Purification of MPF reveals the identity of MPF.

15. MPF = Cyclin B + CDK1

18. Cdc2
Mitotic entry
(Cell Division)
Mitotic Delay
(Cell Growth)

20. No division
Infinite growth
Premature division
Inactive MPFHyperactive MPF

21. Role of Protein Destruction in Cell-Cycle Control

22. Role of APC/C in Cell Cycle Control

24. G1 Phase
Divide or not? That is question

27. Growth Control
Cell should be reached at the specific size to divide
Uncontrolled division leads cancer

29. Integrity of Cellular DNA Monitored by a G1 Checkpoint

31. S-Phase and DNA Replication

36. Metaphase

40. Spindle Checkpoint
If there is unattached kinetocore, stop cell cycle progress