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Proteins in Mitosos and the Cell Cycle :)

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Proteins in Mitosos and the Cell Cycle :)

Postby Statford » Wed Nov 04, 2009 12:03 am

Hey guys! :)

What is the name of proteins, which when phosphorylated, will ubiquitinate cyclin?
What is the name of proteins which, when phosphorylated, promote spindle formation?

I'm really stuck on these questions. =/

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Postby jwalin » Thu Nov 12, 2009 12:09 pm

try searching ubiquitinate cyclin and spindle formation on wikipedia
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Postby sarah90222 » Sat Nov 21, 2009 7:23 pm

i think the first question is APC

is the second one tubulin ...i have no idea.
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Postby jyaron » Mon Nov 30, 2009 5:55 am

Look up the associated proteins of Cyclin A, B, C, D and E, as well as the cyclin-dependent kinases for those proteins (CDK-A, etc..).,

For the second one, you should look at the associated proteins of the MTOC and centriole.
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Postby kolean » Mon Nov 30, 2009 3:10 pm

APC/C and SCF are the ubiquitin-protein ligases for the cell cycle. They themselves are not phosphorylated though. Sic1 is attached to S-phase cyclin/CDK, and when it becomes phosphorylated by the next phase cyclin/CDK, then it is marked for UbQ by SCF. With APC/C, a protein called Cdh1 is attached to the ACTIVE APC/C that ubiquinates mitotic cyclins. When G1 cylin-CDKs are expressed then Cdh1 becomes phosphorylated by them and the Cdh1 then releases the APC/C, making it inactivated.

As far as the proteins that influence the polymerization/depolymerization of tubulin for the spindle formations, they are called MAPs (Microtubule Associated Protein(s)). Dimers of alpha and beta tubulin will dimerize in vitro under NONphysiological conditions. Under in vivo conditions, MAPs are required to stablize or unstabilize the dimer formations. The only thing is that phosphorylation of MAPs makes them disassemble from the tubulin, which then disassembles, thus it does not PROMOTE formation. Dephosphorylation of MAPs promotes formation. In fact some CDKs phosphorylate some of the MAPs to control the cell cycle. Some examples of MAPs is Tau, MAP2, +TIPs, and Stathmin.
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