cytokinesis Flashcards
review: western yew tree, what is it, what is it used for
taxol! derived from the tree and is an inhibitor of cell proliferation by binding MTs so that they are stabalized so that they do not depolymerize
review: saffron, what does it make, what is it used for
colchicine! derived from the saffron to treat gout (uric acid) it binds to tubulin subunits and prevents their polymerization into MTs. May inhibit cell migration of neutrophils to the site of inflammation
what executes cytokinesis? organization?
actin and myosin; contractile ring is built from actin and myosin to pinch off the cell membrane
mitotic cyclin disappears when? important in?
disappears between anaphase and telophase; important in activating early mitotic events
what kinds of regulators work to drive the cell cycle?
protein kinases and protein phoshatases that drive the cell cycle. there are also inhibitors
SMADS control? if bad what happens?
the transcription of the small inhibitors that regulate the cell cycle; if bad, the cell keeps proliferating because it doesn’t turn off.
contractile ring location
typically arises at the cortical cytoplasm where the chromosomes were lined up.
how is contractile ring built?
the cell has to decide where to put the ring, then it brings the machinery to that site. it pinches and the midbody has to do something
what is the scientific research methodology used to study the actin and myosin contractile ring?
show the protein is there, use genetic studies to find the characteristics, take away elements and see what happens
whats cool about cellular slime mold?
its a community of cells; it has signal transduction, it is polarized, it locomotes as a multicellular slug, it comes together to make more slugs
immunocytochemistry needs?
specific antibodies; a dead, sliced cell to see a cell at ONE point of time
green fluorescence protein is good because?
you can take the fluroescence of the natural compound to study a LIVE cell so that you don’t have to kill a cell to study it; it requires NO COFACTORS; it makes a fluorescent center of 3 aa. in the middle of the barrel; it also comes in a multitude of colors
GFP used in what studies?
protein lifespans, gene expression by promotor-reporter fusions, protein protein interactions
what are the three amino acids in the GFP marker?
ser-tyr-gly
where does actin accumulate in a dividing cell?
“cortical site” of the contractile ring
localization doesn’t mean?
localization doesn’t mean that it is doing something there!!
myosin II knock out proves?
you need this to divide the cell!! when it lacks, you make daughter nuclei that are still living in the same cytoplasm because the cell couldn’t make a contractile ring. this is ultimately fatal to the cell
if you put myosin II knock out on a plate, what happens?
it survives because the daughter cells can crawl away and they essentially tear off the original cell. this is called “traction-mediated cytofission”
how does phalloidin relate to cell division?
it binds to filamentous actin and stabalizes it so that it cannot cytokinese because it cannot either form or pinch
remember, what can you use small molecule inhibitors for?
anticancer agents, fungicides, herbicides
Blebbistatin general function?
inhibits blebbies. (cell surface protrusion) blebbies suuper abundant in apoptosis. its a myosin II inhibitor (muscle myosin) it does NOT inhibit myosin I, V etc
Blebbistatin blocks what action? it is used to prove what?
the power stroke of myosin; this proves that actin and myosin are both active in the constriction of the contractile ring. the sister chromatids will separate, but the cell will not cytokinese
purse-string model? the end all model?
at anaphase and telophase, the actin and myosin arrange in a donut, and it pinches together; no. there are other ways to get the cell to pinch as well.
how does the actin and myosin know where to accumulate in a dividing cell?
too much for this card. keep going
rappaport, and sanddollar cell. what does it prove?
he put a glass bead in the middle of the cell to make it a donut but the cell doesn’t care. it divides into a horseshoe, and then divides with an EXTRA contractile ring. the ASTRAL MTs dictate the cytokinesis site
What happened when Mr. Dong Zhang took the nucleus out of a dividing cell? what does it prove?
without the astral mts, it STILL cleaves. this model says the interpolar MTs decide.
overall, what is our main take away for the location of contractile ring?
there are multiple mechanisms that specifiy the plane of division in a cell that needs to cytokinese
players that are specified to go to the contractile ring? What is the major signalling molecule?
hundreds of proteins. Just remember that we have some VIPS like the monomer binders, the things that nucleate filaments, the motor proteins. Gproteins regulate!!!
what kinds of things are G proteins involved in
they are upstring for Ras, Rho,
rho rho rho your boat leads to?
actin ring formation by controlling actin polymerization and the polyermization of myosin that leads to the GTP loaded structure that is ready to go
what did he encourage us to study before the shelf?
turek’s notes. ew.
what if you don’t want to look at turek’s notes?
check out apoptosis in some sort of BRS book because that material will be on both histology and molecular
