Modeling the Budding Yeast Cell Cycle

cln1∆ cln2∆ cln3∆

Simulation:

Change of parameters: ksn2'=ksn2"=0, Dn3=0.
Length of G1 phase: 227 min.
Arrest: G1 arrest according to our rule (see below).

Experiments:

Richardson, H., Wittenberg, C., Cross, F.R. and Reed, S.I. (1989). An essential G1 function for cyclin-like proteins in yeast. Cell 59:1127-1133.
[Abstract] [Article]
Experimental results: Inviable, G1 arrest.
Comments: In the triple-cln (=cln1∆ cln2∆ cln3∆), although START transition is delayed for many hours, eventually the cell grows large enough (in the model) for Clb5-dependent kinase activity to drive [ORI] to 1. This is a serious problem for the model. To account for the inviability of the triple-cln mutant, in this model, we set the following rule for G1 arrest:

A cell must reach [ORI]=1 before the time it takes for a wild type cell in the same medium to divide twice (202.4 min in glucose and 293.4 min in galactose), otherwise it is considered G1-arrested.