The Cell Cycle & Cell Cycle Regulation By Bhuvanesh Kalal

Cell Cycle and Cell Cycle Regulation COMPILED BY: Bhuvanesh S.K. III Sem M.Sc. Microbiology Dayananda Sagar College of Biological Sciences, Bangalore

Acknowledgements Dr. P S Roa Mrs. Shobha K Jayana Divya mam (Guide)

Hithishi mam Sushma mam Dr. John B Mamata B mam Mamata TM mam

OUTLINE 1. Phases of the cell cycle – 1.1 M phase – 1.2 Interphase • 1.2.1 G1 phase • 1.2.2 S phase • 1.2.3 G2 phase – 1.3 G0 phase 2. Regulation of cell cycle – 2.1 Role of Cyclins and CDKs • 2.1.1 General mechanism of cyclin-CDK interaction • 2.1.2 Specific action of cyclin-CDK complexes – 2.2 Cell cycle inhibitors 3. Checkpoints 4 Conclusion 5 References

Phases of the Cell Cycle INTERPHASE (90%) (the cell continuously grows) • G1 phase: gap between M and S phases • S phase: DNA replication • G2 phase: gap between S and M phases

• •

M PHASE (10%) Mitosis: nuclear division Cytokinesis: cytoplamatic division

MITOSIS

Cytokinesis

Real Pictures

Prophase

Metaphase

Anaphase

Telophase

Picture adopted from: http://www.micro.utexas.edu/courses/levin/bio304/genetics/celldiv.html

Real Pictures

Anaphase

Interphase

Prophase Telophase

Metaphase Picture adopted from: http://www.uoguelph.ca/zoology/devobio/210labs/mitosis1.html

Real Pictures

Late Prophase I Metaphase I

Prophase II

Metaphase II

Anaphase I

Anaphase II

Telophase I

Telophase II

Interphase II

Cytokinesis

The comparison of meiosis and mitosis

Cell cycle proteins 1) Cyclins. Activator proteins that are up- or downregulated depending on the phase of the cell cycle. • Cyclin-dependent kinases (CDKs). Serine/threonine kinases that require the binding of a cyclin (or related protein) for full activity. Their range of substrates is not fully defined, but interfering with their activity arrests or slows the cycle. • Cyclin-dependent kinase inhibitors (CKIs). Small peptides that block cyclin/CDK activity either by forming an inactive complex or by acting as a competitive CDK ligand. • DNA replication proteins. DNA polymerases and associated proteins such as proliferating cell nuclear antigen (PCNA) and mini-chromosome maintenance (MCM) proteins, as well as proteins that assure that each origin of replication initiates replication only once per cycle. These include origin recognition complex (ORC) proteins, CDT1 and its suppressor, geminin. • Checkpoint proteins. Members of a network of proteins that monitor DNA integrity and arrest the cell cycle until DNA damage can be repaired.

Leland H. Hartwell

R. Timothy (Tim) Hunt

Sir Paul M. Nurse

The Nobel Prize in Physiology or Medicine 2001 "for their discoveries of key regulators of the cell cycle"

CYCLIN/CDK tyr15-P thr14-P

Regulated by: -tyr15 phosphorylation • inhibitory kinases • activating phosphatases -direct interaction • inhibitor- Wee1 •Activator-Cdc25

P-thr161

cdk1 (cdc2)

cyclin B

(a) Free CDK2 (b) Low-activity cyclin A−CDK2 (c) High-activity cyclin A−CDK2

Regulating a CDK

Regulation 1960 Process Description

1995 Process Description

CONCLUSION • Cancer • Drug target

DISCUSSION ?

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