Introduction to Fungi, Third Edition

SCHIZOSACCHAROMYCETALES
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Fig 9.5 ThecentralroleofCdc2inthecellcycleofS. pombe.The START checkpoint is passed only if Cdc2 is combined with a
G1 cyclin (cig2) and is phosphorylated at a threonine residue at position161 (Thr) but dephosphorylated at a tyrosine residue at
position15 (Tyr).The second major checkpoint is between the G2 and M phases; here Cdc2 needs to be coupled with a G2 cyclin
(Cdc13) and must be phosphorylated at Thr but dephosphorylated at Tyr.The cell cycle is therefore controlled by the type of cyclin
available for coupling with Cdc2, and by the action of kinases such as wee1or mik1and phosphatases (e.g.Cdc25). Adapted from
Lewin (2000).
which stops the cell cycle at the G2/M control
point and commits the cell to apoptosis (selfdestruction)
is DNA damage. This recognition
mechanism is a most important protection
against uncontrolled cell growth (cancer). These
and other implications of the work on the cell
cycle of S. pombe have resulted in the award of
the Nobel Prize for Medicine and Physiology,
among others, to Sir Paul Nurse in 2001. His
Nobel lecture (Nurse, 2002) is a stimulating and
readable account of the unravelling of the cell
cycle in S. pombe.