FIGURE 2.

PER degradation kinetics remain unaltered by the DBT^S mutation. A, timing of the onset of PER degradation in cells co-expressing exogenous DBT (gray, n = 27 cells) or DBT^S (red, n = 28 cells). With DBT, the PER level starts to decrease around 3.4 ± 0.1 h and with DBT^S around 3.4 ± 0.13 h. B, interaction with DBT confers a half-life of 1.20 ± 0.1 h on PER, independent of pre-degradation PER levels. With DBT^S, average PER half-life in S2 cells is 1.24 ± 0.1 h. C, on average, DBT reduces PER to 0.14 ± 0.07 of its pre-degradation levels whereas for DBT^S the fractional drop in PER is 0.17 ± 0.1. The fraction of PER-YFP remaining after degradation is also independent of the initial PER abundance. D, examples of DBT^S temporal variation when co-expressed with PER. DBT^S stability is similar to that of DBT (lower panel).