BIOL 230W Lecture Notes - Lecture 20: Kinetochore, Microtubule, Bub1B
Document Summary
Biol 230w lecture 20 mitotic checkpoint. Replication stalling results in single stranded dna in nucleus. Single stranded dna recruit replication protein a rpa. Entry into mitosis requires cyclin a and b: cdk interaction. Progression past metaphase requires degradation of cyclin a and b and proteins separate chromosomes. Complex of proteins that target other proteins for destruction. Activated by protein cdc20: point of regulation for the metaphase checkpoint. Must inhibit cdk1 function to progress to anaphase: all others so far have required cdk activation. Turned on: unattached chromosomes (anaphase will not occur) Signal: apc/cdc20 inhibitors activated by unattached chromosomes. Chemotherapeutic drugs typically disrupt metaphase: prevents chromosomes from attaching to microtubules. Naked kinetochore activates checkpoint signal: mad2 and bubr1. When apc and cdc20 are active: no checkpoint proteins, degrades securin, degrades cyclin b, allows segregation. Apc not inhibited when all microtubules are bound to kinetochore.
