Normalized comparison of the modified model outputs to K562 data.

<p><b>A, B, D, E, F</b>: total simulated levels (bound and free, inactive and active) of cyclins A and B, and cyclin B/Cdk1 activity (<b>C</b>) are compared to the measured expression profiles of cyclins A2 and B1, and PHH3. <b>D, E</b>: magnified view of early cyclin A and B expression. <b>F</b>: magnified view of the final 3% of the cell cycle. Symbols = data; lines = simulated output. The correlation between PHH3 expression and B cyclin/Cdk1 activity is for mitotic onset only. Since PHH3 is a proxy for B cyclin/Cdk1 activity, there isn’t a rationale for an exact match to the shape on the front side (onset) and we expect the activity to decrease as cyclin B is degraded, whereas it is known that phosphorylation levels of histone H3 (PHH3) decrease after B cyclin degradation (e.g., <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0097130#pone.0097130-Crosio1" target="_blank">[59]</a>).