A bone cancer cell transfected with a fusion gene for GFP-PTHrP. PTHrP is a parathyroid hormone
related protein . Localization of PTHrP (here the fusion protien) in
cytoplasm or nucleus is dependent on cell cycle phases. This sequence of images show
GFP-PTHrP is actively transported from cytoplasm to nucleus after photo-bleaching (FRAP).
The assay is useful in investigating a new drug's mechanisms.