1
Mitotic Spindle
Cell from Newt lung in prometaphase
2
Some Major Events of Mitosis
•Centrosome duplication (G2).
•Mitotic spindle formation (prophase).
•Chromosome condensation (prophase).
•Breakdown of nuclear envelope
(prometaphase).
•Chromosome attachment to MTs
begins (prometaphase).
•The metaphase plate.
•Anaphase.
The Centrosome
Cycle
3
Increased Dynamic Changes
(Kinesins)
M–Cdk
¯MAP activity
“Kinesin activity
“Dynamic changes of MTs
Recall from previous lecture:
(by phosphorylation)
4
Components of the Mitotic Spindle
1. Microtubules
•Astral
•Kinetochore
•Overlap
2. Motor proteins
•Kinesin–related (+)
•Dynein (-)
3. Chromosomes (chromatids)
4. Centrosome
•Centrioles
•PCM
5
Motor Proteins Contribute to Spindle Assembly
•Multimeric motor proteins “cross–link” antiparallel MTs.
•(+) end–directed kinesin–related proteins (KRPs, e.g.
BimC or kinesin–5).
•KRPs self–associate with each other at their tail domains.
•Slide overlap MTs past each other.
•Promotes elongation of mitotic spindle.
6
Motor Proteins Contribute to Spindle Assembly
•Motor proteins cross–link adjacent MTs.
•Multimeric (–) end–directed dyneins and kinesin–14
arrange minus ends.
•Creation of foci at spindle poles.
Spindle Pole Separation
•Prophase
