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ISABEL ÁLVAREZ-TABARÉS Y COLS. ANAL. REAL ACAD. NAC. FARM.

FIGURE 6. Involvement of Dis2 and Wsh3 in polarised tip growth.
Recruitment of Dis2 to the cell tips by Wsh3 is required for the maintainment of

polarised tip growth, most likely due to the modulation of the F-actin
cytoskeleton.

recovery from stress echoes the requirement for phosphorylation of
the polo kinase Plo1 on serine 402 to promote tip growth during
recovery from centrifugation and heat stress (79). However, it
remains to be established whether Dis2 counteracts the action of
polo kinase or any of the other protein kinases, such as Pom1, Kin1,
Pck2 and Pck3 that modulate cell morphogenesis in fission yeast
(80-82). Alternatively it could play a critical role in modulating the
activity of the kinases of the stress response pathway that associates
with Wsh3/Tea4 (27). In this scenario the impact on morphogenesis
would be mediated by stress signalling to either halt growth in the
initial response to the stress, or to re-initiate it once cell composition
has been changed to deal with this altered state.

Although Bud14/Glc7 is required for spindle orientation rather
than cell morphogenesis the conservation of Bud14 related molecules
across species indicates that the identification of the substrates of
the Dis2-Wsh3/Tea4 holoenzyme and clarifying its relationship with
the cell polarity/morphogenesis kinases will shed much light on the
control of the microtubule cytoskeleton and cell morphogenesis by
protein phosphorylation.

FUTURE PERSPECTIVES

The field of protein phosphorylation research has entered a new
era for several reasons. First, because of what is a nearly complete
list of catalytic subunits in several organisms, it is now possible to
do functional genomic screens for the role of phosphatases in specific
biological processes. Second, as more phosphatase-targeting subunits

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