Figure 3.

Mapping of the rhythm-generating element by using deletion mutants of Per2. (A) Transcriptional oscillation of a series of mPer2-luc 10-base pair deletion constructs was monitored in real time. NIH3T3 cells were transfected and then stimulated with a high concentration of serum. Peak values of the curves were set to 1 (vertical scale: relative cpm; horizontal scale: 1440 min = 1 d). A representative result of three independent experiments is shown. For accurate comparison, thin lines show the curve for “mPer2-luc (-105).” (B) Schematic representation of the results obtained from the 10-base pair deletion analysis, taken together with those in Figure 2. Sequence inspection reveals an E-box-like sequence (CACGTT) in the region essential for circadian transcription of Per2.