SELECTION SYSTEM FOR GENES ENCODING NUCLEAR-TARGETED PROTEINS

Nuclear proteins have essential roles in cell proliferation and differ entiation. We have developed a yeast selection system-the nuclear tran sportation trap (NTT)-to identify genes encoding nuclear transport sig nals. Both unknown and previously identified nuclear localization sign als were identified from a human fetal brain cDNA library. The majorit y (75%) of the unknown proteins examined were exclusively localized to the nucleus in COS-7 cells. We propose that NTT is an efficient metho d for isolating cDNAs that encode nuclear targeted proteins that can b e applied to the retrieval of novel nuclear proteins and to annotate g ene function.