C. Enenkel et al., EXPRESSION IN YEAST OF BINDING REGIONS OF KARYOPHERIN-ALPHA AND KARYOPHERIN-BETA INHIBITS NUCLEAR IMPORT AND CELL-GROWTH, Proceedings of the National Academy of Sciences of the United Statesof America, 93(23), 1996, pp. 12986-12991
Using truncated forms of recombinant yeast karyopherins alpha and beta
in in vitro binding assays, se mapped the regions of karyopherin alph
a that hind to karyopherin beta and the regions of karyopherin beta th
at interact with karyopherin alpha and with Ran-GTP. Karyopherin alpha
's binding region for karyopherin beta was localized to its N-terminal
domain, which contains several clusters of basic residues, whereas ka
ryopherin beta's binding region for karyopherin alpha was localized to
an internal region containing two clusters of acidic residues, Karyop
herin beta's binding region for Ran-GTP overlaps with that for karyoph
erin alpha and comprises at least one of the two acidic clusters requi
red for karyopherin alpha binding in addition to further downstream de
terminants not required for karyopherin alpha binding, Overexpression
in yeast of fragments containing either karyopherin beta's binding reg
ion for alpha and Ran GTP or karyopherin alpha's binding region for be
ta resulted in sequestration of most of the cytosolic karyopherin alph
a or karyopherin beta, respectively, in complexes containing the trunc
ated proteins. As these binding region-containing fragments lack other
domains required for function of the corresponding protein, the overe
xpression of either fragment also inhibited in vivo nuclear import of
a model reporter protein as well as cell growth.