Reversible tyrosine phosphorylation and cell cycle control

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Reversible tyrosine phosphorylation regulates eukaryotic cell growth and the cell division cycle.
• The protein kinase p34cdc2 activity, essential for mitosis entry, is controlled by tyrosine 15 phosphorylation.
• Protein kinases and phosphatases form a network regulating p34cdc2 phosphorylation and cell cycle progression.

Purpose of the Study:

• To review the roles of key protein kinases and phosphatases in regulating cell division.
• To highlight the genetic approaches used in fission yeast to identify these regulators.
• To underscore the conserved nature of tyrosine phosphorylation in cell cycle control across eukaryotes.

Main Methods:

• Genetic approaches in Schizosaccharomyces pombe to identify genes encoding cell cycle regulators.
• Focus on specific protein kinases: wee1+, mik1+, cdr1+/nim1+.
• Focus on specific protein phosphatases: cdc25+, pyp1+, pyp2+, pyp3+.

Main Results:

• Identification of several key protein kinases and phosphatases involved in p34cdc2 regulation.
• Demonstration of a complex regulatory network controlling tyrosine phosphorylation.
• Evidence for conserved mechanisms of cell cycle regulation in higher eukaryotes.

Conclusions:

• Reversible tyrosine phosphorylation is a fundamental mechanism for cell division cycle control.
• The identified kinases and phosphatases play critical roles in regulating mitosis entry.
• Conserved regulators highlight the universal importance of this phosphorylation-based system.