BIOL 201 Lecture Notes - Lecture 29: Mad1, Cdc20, Securin
23 Jul 2018
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Document Summary
Proteins are tagged for the proteasomes by poly-ubiquitination: unfolded by atpase at the top of proteasome, cut up by the proteasome and fragments are released. As soon as you release the binding partners, they bind to apcs. Therefore, cells control the exit of mitosis by holding back the metaphase-anaphase transition. Inhibitions of apc partners allow for control of the exit of mitosis. Absence of cdc20 led mutants to have an abnormal transition to anaphase. In the presence of cdc20, apc polyubiquitinates securin. Ubiquitination pops chromosomes apart: after anaphase, cdh1 gets activated. Anaphase needs to wait until sister chromatids are bi-oriented: bi-oriented when: Centromeres of each sister is connected to opposite spindle poles with microtubules. Waiting prevent proteolysis of cohesin rings which are holding sister chromatids together while the others position themselves: when it"s time to open the cohesin, separase comes to cut the scc1 domain. Separase is regulated by securin, which occludes the catalytic cleft of separase.
