The nuclear import of p53 is determined by the presence of a basic domain and its relative position to the nuclear localization signal

It has been reported that Lysine-305 is needed for the nuclear import of th e p53 protein (Liang et al., 1998). In the present study, further mutagenes is analyses were carried out between Lys-305 and the major nuclear localiza tion signal (NLS I) of p53. It was found that a single mutation of Arg-306 resulted in the defect of p53 nuclear import. This effect is the same as th at of Lys-305 mutation. Other mutations between Arg-306 and NLS I have no e ffect on the nuclear import of p53. However, deletions of more than two ami no acids between this region abolished the transport of p53 into the nucleu s. These results indicate that a basic domain other than the well defined N LS is required for the nuclear import of p53. A spacer between this basic d omain and NLS I is necessary for the entrance of p53 into the cell nucleus.