Ma. Heine et al., THE GLY ARG-RICH (GAR) DOMAIN OF XENOPUS NUCLEOLIN FACILITATES IN-VITRO NUCLEIC-ACID BINDING AND IN-VIVO NUCLEOLAR LOCALIZATION/, Molecular biology of the cell, 4(11), 1993, pp. 1189-1204
Epitope-tagged Xenopus nucleolin was expressed in Escherichia coli cel
ls and in Xenopus oocytes either as a full-length wild-type protein or
as a truncation that lacked the distinctive carboxy glycine/arginine-
rich (GAR) domain. Both full-length and truncated versions of nucleoli
n were tagged at their amino termini with five tandem human c-myc epit
opes. Whether produced in E. coli or in Xenopus, epitope-tagged full-l
ength nucleolin bound nucleic acid probes in in vitro filter binding a
ssays. Conversely, the E. coli-expressed GAR truncation failed to bind
the nucleic acid probes, whereas the Xenopus-expressed truncation mai
ntained slight binding activity. Indirect immunofluorescence staining
showed that myc-tagged full-length nucleolin properly localized to the
dense fibrillar regions within the multiple nucleoli of Xenopus oocyt
e nuclei. The epitope-tagged GAR truncation also translocated to the o
ocyte nuclei, but it failed to efficiently localize to the nucleoli. O
ur results show that the carboxy GAR domain must be present for nucleo
lin to efficiently bind nucleic acids in vitro and to associate with n
ucleoli in vivo.