PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Chapter 19 – The Eukaryotic Cell Cycle19.3. Regulation of CDK activityTypes of cyclins and cyclin-dependent kinases (CDKs)CDKs are regulated a few different ways1) Binding to a particular cycli n2) Phosphorylation3) Binding to an inhibi torCyclins are r egulate d a few diffe rent ways1) Binding to a particular cdk2) Production3) Degradation-SCF-APC/C19.4. Cell cycle entryE2F transcription factorsDegradation of S phase CDK inhibitor triggers DNA replication-SCF ubiquitin ligaseDuplicating chromosomes - Replication at each origin starts only onceTethering of sister chromatids by cohesins19.5. Entry into MitosisFunctions of the mitotic cyclin (cyclin B/cdk1)1) Breakdown of nuclear pore complexes (in prophase) Phosphorylates specific nucleoporins2) Nuclear envelope breakdown – via release of lamin filaments.19.6. Completion of Mitosis: Chromosome Segregation and Exit1) APC/C and ubiquitination during anaphaseAPC/C and ubiquitination at the end of mitosisCdc14 phosphatase – removes Ps from mitotic cyclin-cdks19.7. Surveillance MechanismsCheckpoints – ensure that chromosomes are intact and each stage is completed before the next stage occurs.1) DNA-damage checkpoint:2) DNA replication checkpoint – prevents activation of cyclin B/cdk13) Spindle assembly checkpoint:4) Spindle-position checkpoint: uses Cdc14 phosphataseIn interphase and early mitosis, Cdc14 is sequestered in the nucleolus. Key protein is