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My name is Tomo Tanaka, I'm going to discuss mechanisms of chromosome
bi-orientation in budding.
In 2009, my colleague Professor Mike Stark gave a Henry Stewart talk
about this topic.
In my talk today, I would like to update the information on this topic,
and then discuss a recent finding.
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The diagram here shows how kinetochore-microtubule interaction is
formed in a step-wise manner, during early mitosis.
In step 1 the kinetochore (represented by the orange dot) is loaded on
the lateral side of a microtubule extending from a spindle pole,
forming the lateral attachment, as shown in step 2.
The kinetochore slides along the microtubule towards the spindle pole,
subsequently that kinetochore is tethered at the microtubule end,
forming the end-on attachment in step 3.
The kinetochore moves further towards the spindle pole,
as the microtubule depolymerisation proceeds.
In step 4, both sister kinetochores often attach to microtubules from the same
spindle pole, forming an aberrant attachment.
Subsequently, such aberrant attachments must be resolved through
the error correction process, shown in step 5.
When sister kinetochores attach to microtubules from the opposite pole,
bi-orientation is established, then kinetochore-microtubule interactions
are stabilised (in step 6).
My talk focuses on steps 4, 5, and 6, how aberrant attachment is resolved
through the error correction process, to establish bi-orientation.
Aurora B kinase (which is also called Ipl1) in budding yeast is the main
regulator for the resolution of aberrant kinetochore-microtubule interactions.
I will discuss how Aurora B kinase promotes error correction
for bi-orientation, more specifically I'll talk about:
targets of Aurora B for error correction in the context of yeast kinetochore structure;
differential regulation of lateral and end-on attachment by Aurora B;
regulation of Aurora B localisation at the centromere and inner kinetochore;
and a spatial separation model for Aurora B-dependent error correction.
In addition to Aurora B, other factors also facilitate error correction
for bi-orientation.
I will discuss how other factors promote error correction for bi-orientation,
in particular I'll talk about changes of microtubule dynamics,
and the rôles of Stu2 in error correction.
