A 2003 study split a Xenopus laevis egg extract into portions with different histories. One received calcium to destroy endogenous cyclin B before receiving nondegradable cyclin B; the other received nondegradable cyclin B first, then calcium. The same sustained cyclin B dose was approached from low or high Cdc2 activity. A phosphorimager quantified histone H1 phosphorylation, sampling every – minutes until an apparent stationary response. At –, the dose maintained high activity but failed to induce it from the low state.[ref]
Controls tracked labeled endogenous cyclin B disappearance after calcium treatment and persistence of nondegradable cyclin B, addressing unequal remaining input. The comparison supports hysteresis under extract conditions; finite observations cannot establish indefinite persistence. It does not isolate each reinforcing path or establish thresholds in intact biological cells.[ref]
Building a cell cycle oscillator: hysteresis and bistability in the activation of Cdc2 by Joseph R. Pomerening and others. p. 3, control discussion; p. 4, Figure 3h; reported 60–90 minute approach to apparent steady state
A Xenopus laevis egg extract is a preparation of egg contents retaining biochemical machinery of the cell cycle outside intact biological cells.
Histone H1 is the protein used as a substrate for the Cdc2 activity readout in the cell-cycle hysteresis experiment.
Articles by others on the same topic
There are currently no matching articles.