U. Boehm et al., ONE OF 3 NUCLEAR-LOCALIZATION SIGNALS OF MAIZE ACTIVATOR (AC) TRANSPOSASE OVERLAPS THE DNA-BINDING DOMAIN, Plant journal, 7(3), 1995, pp. 441-451
The nuclear localization sequences (NLSs) of the Ac transposase (TPase
) protein have been characterized by indirect immunofluorescence detec
tion of TPase deletion derivatives and TPase/beta-glucuronidase (GUS)
fusion proteins in transiently transfected Petunia cells. The TPase co
ntains three NLSs near its amino-terminal end, NLS(44-62), NLS(159-178
) and NLS(174-206), each of which is sufficient to redirect GUS to the
nucleus. Deletion of the N-terminal 102 TPase residues including NLS(
44-62) results in strongly reduced nuclear import of the truncated TPa
se. NLS(44-62) and NLS(159-178) are bipartite NLSs, whereas the struct
ure of NLS(174-206) does not allow a classification into one of the th
ree major NLS categories. NLS(174-206) overlaps with the basic DNA-bin
ding domain of TPase. A substitution of two amino acids in this segmen
t (His(191)-->Arg and Arg(193)-->His) results in a total loss of DNA-b
inding activity, but retains reduced NLS activity. Accordingly, the tw
o functions can be separated. In addition, we show that a NLS-deficien
t 71 kDa TPase derivative is co-imported into the nucleus in the prese
nce of wild-type TPase.