Figure 1.

Physical interaction of mPER proteins after serum shock. Heterodimerization detected by the immunoprecipitation in combinations mPER1–mPER3, (A), mPER2–mPER3, (B) and mPER1–mPER2. (C) Treatment with high concentrations of horse serum accelerates the heterodimerizations among mPERs in all combinations. No change was noted in the amount of mPER3-Myc (A, bottom) and mPER2-Flag (B, bottom) in total cell lysates showing that serum shock does not increase the amount of expressed proteins. (D) Homodimerization detected by immunoprecipitation. mPER2 and mPER3 form homodimers, but mPER1 does not homodimerize to a significant degree; serum shock has no effects on homodimerization.