FIG. 9.

Characterization of an NLS in the N-terminal domain of the 34-kDa FGF-2. (A) Amino acid sequence of the NH2-terminal domain of the 34-kDa FGF-2 (78 amino acid residues). The boldface boxed characters represent the amino acids that were deleted in construct F34ΔNCAT. (B) Subcellular distribution of different chimeric CAT proteins was analyzed either by immunocytolocalization in transfected COS-7 cells (fluorescent staining micrographs in the middle) or by fractionation of transfected SK-Hep-1 cells into nuclear and cytosolic extracts (histograms on the right), as described in Materials and Methods. SVCAT fusion contains the minimal SV40 large-T antigen NLS (PKKKRKV [24]). F18- and F24CAT chimeras have N-terminal parts corresponding to the 20 and 75 N-terminal amino acid residues of 18- and 24-kDa FGF-2, respectively. The latter includes the 24-kDa FGF-2 NLS described previously (1). The F34CAT chimera contains the 78-amino-acid N-terminal domain of the 34-kDa FGF-2 shown in panel A. F34ΔNCAT has a deletion of the arginine-rich box shown in panel A, corresponding to residues 43 to 49. Results from immunocytolocalization and cell fractionation are presented at the right for each chimeric protein and the control (CAT). The subcellular distribution between nucleus and cytosol is represented as a percentage of the total CAT activity measured.