Figure 7.9 Regulation of the Cell Cycle
Initial investigations into the regulation of the cell cycle involved a number of cell fusion experiments in which cells in different stages of the cell cycle were fused together to determine if the contents of one cell could exert control over another cell. To test the hypothesis that a cell in S phase contains an activator of DNA replication, an S phase cell was fused with a cell in G1 phase. Results showed that the fused cell, which contained two nuclei, was induced to enter S phase, suggesting that a substance produced by the S phase cell diffused to the G1 nucleus and activated DNA replication. Additional experiments were used to demonstrate the existence of a positive regulator of mitosis, first called maturation-promoting factor (MPF). Researchers performed cytoplasmic injections to show that cytoplasm taken from cells in M phase could induce other cells to complete mitosis. Similarly, when a cell in M phase was fused with a cell arrested in G1 phase, the fused cells underwent mitosis. Later studies went on to demonstrate that it is the Cdk/cyclin complex that is actually responsible for cell cycle progression.
Original Papers
Rao, P. N., and R. T. Johnson. 1970. Mammalian Cell Fusion: Studies on the Regulation of DNA Synthesis and Mitosis. Nature 225: 159–164.
http://www.nature.com/nature/journal/v225/n5228/pdf/225159a0.pdf
See also an excellent overview of cell cycle research:
Stillman, B. 1996. Cell Cycle Control of DNA Replication. Science 274: 1659–1664.
http://www.jstor.org/stable/2890937
http://dx.doi.org/10.1126/science.274.5293.1659
Links
Kimball’s Biology Pages: The Cell Cycle
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellCycle.html
Nature publishing group: Web focus on cell division: One-way traffic
http://www.nature.com/celldivision/milestones/full/milestone06.html
Nobel Prize.org: Control of the Cell Cycle
http://nobelprize.org/educational_games/medicine/2001/
Cells Alive: The cell cycle
http://www.cellsalive.com/cell_cycle.htm
University of Southern California: Dr Forsburg’s all-purpose Cell Cycle Lecture Notes
http://www-rcf.usc.edu/~forsburg/cclecture.html
The Cell: A Molecular Approach: Regulators of Cell Cycle Progression
http://www.ncbi.nlm.nih.gov/books/NBK9962/
Web Books: MPF and the Initiation of Mitosis
http://www.web-books.com/MoBio/Free/Ch8B2.htm