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

supported by the work of Shang and colleagues (58). They have
shown that the interactions between Dam1 and Spc34 (a subunit of
the Dam1 complex) and Ndc80 (a subunit of the Ndc80 complex),
are weakened by mutations mimicking phosphorylation at Ipl1 sites
(58). A model has been proposed in which phosphorylation
of essential kinetochore components, such as Dam1 and Ndc80
complexes, weakens their physical interactions and therefore re-
sults in the detachment of the kinetochore from microtubules.
Dephosphorylation by Glc7 enables the re-association of the DASH
complex with the kinetochore. This process of dissociation and
reassociation may facilitate the re-orientation of kinetochores
and may continue until bi-orientation is eventually established
(Figure 4).

FIGURE 4. Model for phosphoregulation at the yeast kinetochore. Interactions
between the Dam1 complex and the Ndc80 complex are proposed to be weakened

when Dam1 and Ndc80 are phosphorylated by Ipl1. The weakening of this
association facilitates the subsequent establishment of new kinetochore-

microtubule attachments and the establishment of bipolar attachment. Glc7 might

be counteracting Ipl1. Model adapted from (56) and (58).

POSSIBLE FUNCTIONS OF DIS 2 IN ENDOCYTOSIS

The extensive characterisation of endocytosis in S. cerevisiae
provides a framework within which to view Dis2 association with

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