Analysis of cell cycle regulation using Aspergillus nidulans

Aspergillus nidulans has proved to be an excellent model system to help unravel the genetic and biochemical control systems that regulate the cell cycle. Many genes that specifically affect progression through G2 into mitosis have been isolated. Study of these genes has helped to formulate concepts about how the cell cycle is regulated. The existence of regulatory networks involving protein phosphorylation and dephosphorylation has been realized, and how the kinases and phosphatases of these networks ensure correct order and timing through the cell cycle is beginning to be understood. Our studies indicate that activation of two protein kinases is essential for progression into mitosis. One, the universal p34cdc2 H1 kinase, has been well studied in many systems and is considered the key activator of mitotic initiation. However, in the absence of the NIMA protein kinase p34cdc2 cannot promote mitosis. How these two mitotic kinases interact is therefore of great importance to our understanding of cell cycle regulation. The contribution of studies using A. nidulans to the formulation of concepts about how the cell cycle is regulated is the topic of this paper. Key words: Aspergillus nidulans, cell cycle regulation, protein kinase, NIMA, p34cdc2, cyclinB, Cdc25.