Characterization of bioluminescent CycE-Luc2 reporter for the G1 phase in HeLa cells. (A) Schematic diagrams of CycE-Luc2 constructs. The recombinant plasmid CycE-Luc2 encoding cyclin E cDNA fused in-frame at the N termini of luciferase 2 cDNA under the control of the CMV promoter. (B) CycE-Luc2 fusion protein was expressed in transfected HeLa cells by immunoblotting. (C&D) Different clones of stable expressed CycE-Luc2 was established and imaged using the IVIS Lumina imaging system to obtain FLUX measurements (C) and quantitated (D). (E&F) HeLa-CycE-Luc2 clone 2 cells were serially diluted, placed into wells of a 24 well plate, and immediately imaged using the IVIS Lumina imaging system to obtain FLUX measurements (E), and a plot comparing total flux to cell number was generated (F). (G-I) HeLa-CycE-Luc2 clone 2 cells were arrested in G2/M phase by growth in Nocodazale (0.4 µg/mL L). After removing Nocodazale to release G2/M cell cycle arrest, the alteration of the luciferase activity was measured at various time points (G). Meanwhile, the cell content (H) and cell cycle distribution (I) were analyzed by flow cytometer and quantitated. All the groups have four replicates and the experiments were repeated for three times. Error bars indicate standard error.