FIG. 3.

Removal of the conserved sequence weakens transcriptional repression activity of PER protein. This defect could be from reduction in nuclear localization as well as independent of the change in subcellular localization; these possibilities are not mutually exclusive. (a) Repression activity of PER and PERΔ from S2 cell reporter assay, with increasing amounts of PER. The graph represents normalized luciferase activity, which is inversely related to the repression activity. (Bottom) Western blots of PER and p150 (as a loading control) are shown. (b) Percentages of S2 cells with distinct nuclear PER staining, without or with nuclear export inhibitor LMB, which suggests that PERΔ is defective at both the nuclear entry and export levels. (c) Repression activity of PERΔ is moderately stronger with the application of LMB, though still weaker than that of wild-type PER, which implies that the reduction of the repression activity could be either dependent on or independent of nuclear localization.