Two coilin truncation mutants localize to the
nucleolus and CBs, but do not mis-localize endogenous coilin, snRNPs,
or SMN to the nucleolus. (A) GFP-coilin(1–248) and GFP-coilin(1–315)
mutants, upon transfection into HeLa, were found to have identical
nucleolar and CB expression profiles. Antibodies to fibrillarin and
Nopp140, which normally localize in nucleoli and CBs, reveal complete
colocalization with these proteins. Endogenous coilin localization was
determined in GFP-coilin(1–248) transfected cells using anticoilin
antibodies that recognize epitopes downstream of the truncation. Note
that endogenous coilin is not mislocalized to the nucleolus in
GFP-coilin(1–248)transfected cells. (B and C)
GFP-coilin(1–248) transfected cells were assessed for the localization
of Sm proteins (B) and SMN (C). No nucleolar accumulations of snRNPs or
SMN were observed. As expected, accumulations of snRNPs could be
detected in the CBs (arrows). Likewise, SMN is present in the CB foci
of GFP-coilin(1–248) transfected cells (our unpublished results).
However, a small fraction of GFP-coilin(1–248) cells did not display
CBs, yet SMN foci, or gems, are present in these cells (C).