Modeling the Budding Yeast Cell Cycle

Predictions (vii):

Viability of the triple mutant cdc20∆ clb5∆ pds1∆ depends on a feedback loop that activates Cdh1 at the end of the cycle. (When chromosomes come into alignment on the mitotic spindle, Cdc15 is activated, which in turn activates Cdc14, which activates Cdh1, which eliminates Clb2.) If we perturb elements in this loop, we are likely to render cdc20∆ clb5∆ pds1∆ inviable. On the other hand, the viability of cdc20∆ clb5∆ pds1∆ does not depend on CKIs.

Genotype Phenotype

cdc20∆ clb5∆ pds1∆

triple-deletion + 1.5X NET1
(or 0.5X CDC15, or 0.5X CDC14)

triple deletion + bub2∆

triple deletion + sic1∆
(or cdc6∆2-49, or both)

Viable (Shirayama et al., 1999).

Arrests in telophase (prediction)


Arrests in G1 (prediction).

Viable (prediction).

cdc20∆ clb5∆ pds1∆ is viable

  • cdc20∆ clb5∆ pds1∆+50% of Net1 (or -50% of Cdc15 or Cdc14) is inviable. The level of Cdc14 is critical in these mutants. If there is not enough Cdc14 to compete against Clb2 in Cdh1 activation, the mutant will remain in telophase.

  • cdc20∆ clb5∆ pds1∆ bub2∆ arrests in G1.

  • cdc20∆ clb5∆ pds1∆ sic1∆, (or cdc6∆2-49 or both) is still viable.

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