Fig. 6. At early timepoints, YFP-SmB can exit the nucleus into the cytoplasm. (A,B) HeLa cells expressing YFP-SmB for 24 hours were bleached repeatedly using a region of interest including a region of the cytoplasm of one cell and a region of the nucleus of its neighbour (rectangle in first image). The cells were imaged following each bleach event. In the cell undergoing bleaching of the nucleus, the entire nucleus was rapidly depleted of YFP-SmB. In the cell undergoing cytoplasmic bleaching, the nucleus also lost a significant amount of the nuclear signal. Bar, 22 µm. (C) Intensity of YFP-SmB signal in the nucleus (outside the bleached region) for the two bleached cells in A against time. (D) Intensity of YFP-SmB in a CB and a region of the nucleoplasm in a cell undergoing cytoplasmic bleaching demonstrates that signal is lost equally from the CB and the nucleoplasm.