Fluorescence screening, protein purification and subcellular localization. (A) Fluorescence screening in bacterial colonies using the leak expression of the target protein fused with Venus. A non-fluorescent colony is identified by arrow 1; a fluorescent colony, by arrow 2. (B) The purification of the 6xHis-Venus-GST construct (identified by the arrow). Lane MW is the molecular weight marker; lane 1, the cell lysate; lane 2, the elusion from the Ni-NTA column; lane 3, the elusion from the GST column. All vectors were transfected into COS-7 cells for fluorescence imaging. The 10× magnification of (C) the cytoplasmic distribution of the 6xHis-Venus-GST and (E) the endoplasmic distribution of Venus N-terminally fused with the interleukin-4 leader sequence and C-terminally fused with the KDEL retention signal. (D) The 40× magnification of the nucleolar distribution of Venus N-terminally fused with the HIV Tat domain.