Partitioning of chromatids during mitosis requires that chromosome
compaction and spindle length scale appropriately with each other. However,
it is not clear whether chromosome condensation and spindle elongation are
linked. Here we have used chromosome fusions to examine the impact of
increased chromosome length during yeast mitosis. We find that yeast cells
could cope with a >50% increase in the length of their longest chromosome
arm by decreasing the physical length of the mitotic chromosome ...
Partitioning of chromatids during mitosis requires that chromosome
compaction and spindle length scale appropriately with each other. However,
it is not clear whether chromosome condensation and spindle elongation are
linked. Here we have used chromosome fusions to examine the impact of
increased chromosome length during yeast mitosis. We find that yeast cells
could cope with a >50% increase in the length of their longest chromosome
arm by decreasing the physical length of the mitotic chromosome arm through
1) reducing the number of copies of the repetitive rDNA array and 2) by
increasing the level of mitotic condensation. Consistently, cells carrying the
fused chromosomes became more sensitive to loss of condensin- and its
regulator polo kinase/Cdc5. Length-dependent stimulation of condensation
took place during anaphase and depended on aurora/Ipl1 activity, its
localization to the spindle midzone, and phosphorylation of histone H3 on
Ser10, a known Ipl1 substrate. The anaphase spindle therefore may function
as a ruler to adapt the condensation of chromosomes to spindle length.
Consistent with this, chromosome condensation levels correlate with the
length of anaphase spindles.
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