Advanced Cell Biology

2014 1nd Semester

Department of Animal Science

Chungbuk National University

8th Lecture

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

Cell Cycle

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.

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

Cyclin and Cyclin Dependent Protein Kinase

Discovery of Cyclin and Regulators

- Temperature Sensitive Yeast mutant defective in Cell Cycle

- Isolations of cdc mutants

Xenopus embryo as model system for Cell Cycle Research

Xenopus egg extract as in vitro model forCell Cycle Research

Maturation Promoting Factor (MPF)

Some protein(?) factors inducing Nuclear Membrane Breakdown and spindle Formation

Purification of MPF reveals the identity of MPF..

MPF = Cyclin B + CDK1

Cdc2

Mitotic entry(Cell Division)

Mitotic Delay(Cell Growth)

No divisionInfinite growth

Premature division

Inactive MPFHyperactive MPF

Role of Protein Destruction in Cell-Cycle Control

Role of APC/C in Cell Cycle Control

G1 Phase

Divide or not? That is question

Growth Control

Cell should be reached at the specific size to divideUncontrolled division leads cancer

Integrity of Cellular DNA Monitored by a G1 Checkpoint

S-Phase and DNA Replication

Metaphase

Spindle Checkpoint

If there is unattached kinetocore, stop cell cycle progress