The invention provides methods of determining the presence of a nuclear localization
signal and/or the presence of a nuclear export signal in a protein of interest.
The invention further provides chimeric nucleic acids and recombinant host cells
for use in such methods. Additionally provided is a nucleic acid molecule encoding
a modified LexA protein, wherein the modified LexA protein has no nuclear localization
signal, as well as the modified LexA protein itself. In the nuclear import assay,
if a protein of interest fused to a mLexA-Gal4AD hybrid contains a functional
NLS, the fusion product will enter the yeast cell nucleus and activate the expression
of reporter genes. In the nuclear export assay, if a protein of interest fused
to a mLexA-SV40 NLS-Gal4AD hybrid contains a functional NES, the
fusion product localized to the cell nucleus will exit into the cytoplasm, decreasing
the reporter gene expression levels.
