MCD BIO 165A Chapter Notes - Chapter microtubules: Spindle Apparatus, Motor Protein, Dynein
22 Nov 2018
School
Course
Professor
vid
microtubule & motor proteins
Mitotic spindle
• MT & motor proteins coordinate chromosomal separation during cell division
• Originate from centrioles on poles of cell -> platform of MT polymerization in all
directions
• Stability & motility of MT/spindle depends on motor proteins: kinesin & dynein
• (astral) MT interacting with cell periphery connected to cell membrane thru proteins.
dyneins binding directly MT to adaptor proteins
- Spindle rotation/orientation enabled by dynein
- Dynein orienting spindle critical to how plane of cell division occurs & where daughter
cells will be located (parallel/on top of each other) -> important to tissue
morphogenesis
• Additional motor proteins stabilize spindle
- MT interact & stabilized thru kinesin
- MT binding to chromosome coordinated & stabilized thru both kinesin & dynein
• 3 types of MT
- Astral MT: interact with protein & membrane; orienting spindle
- Polar MT: provide stability to spindle & interact with each other thru kinesin
- Kinetochore MT: bind to DNA thru kinetochore
Astral MT
• 2 major functions:
- spindle orientation -> plane of cell division (aided by dynein)
- symmetric/asymmetric cell division -> cell fate
• Can be identical/differing length on each pole
• Uneven cytoplasm & organelle distribution determines cell size -> asymmetric cell
division
• Bottom: stem cell; upper: neuroblast
• Orientation
- Orientation made possible by MT interaction with dynein & dynein with adaptors in
cell periphery
MT interact with DNA
•
- DNA first captures MT
- Pink chromosome (in this case) only bound to MT from one pole; needs to find the
other one to get adequate chromatid separation
- Position of chromosome towards metaphase plate requires MT polymerization &
depolymerization, and motor proteins
- Motor proteins interact with DNA and MT -> push/pull to achieve chromatid
positioning
- Dynein walks to – end: pull
- Kinesin walks to + end: push
• Step-wise
Document Summary
Dynein orienting spindle critical to how plane of cell division occurs & where daughter. Spindle rotation/orientation enabled by dynein cells will be located (parallel/on top of each other) -> important to tissue morphogenesis: additional motor proteins stabilize spindle. Mt binding to chromosome coordinated & stabilized thru both kinesin & dynein: 3 types of mt. Astral mt: interact with protein & membrane; orienting spindle. Polar mt: provide stability to spindle & interact with each other thru kinesin. Kinetochore mt: bind to dna thru kinetochore. Orientation made possible by mt interaction with dynein & dynein with adaptors in cell periphery. Pink chromosome (in this case) only bound to mt from one pole; needs to find the other one to get adequate chromatid separation. Position of chromosome towards metaphase plate requires mt polymerization & depolymerization, and motor proteins. Motor proteins interact with dna and mt -> push/pull to achieve chromatid positioning. Kinesin walks to + end: push: step-wise.
