Fig. 1. (i) YFP-SmB colocalizes with endogenous Sm proteins in cells from line YFP-SmBE1. Maximum intensity projections of deconvolved serial sections through cells from line YFPSmBE1 in interphase (A,B) and telophase (C,D). The YFPSmB protein (A,C) colocalizes with endogenous Sm proteins (B,D) in Cajal bodies (arrowheads) and speckles (arrows). Bar, 10 µm. (ii) YFP and CFP-SmB are expressed as single fusion proteins at levels lower than endogenous SmB. SDS-PAGE analysis of whole cell lysates from lines YFPSmBE1, CFPSmBE8.8, parental HeLa cells and HeLa cells transiently transfected with a plasmid encoding YFP. An antibody to G/YFP (left-hand panel) showed a single band at 30 kDa in cells expressing YFP alone and single bands at the size predicted for YFPSmB or CFPSmB (58 kDa) in cells from lines YFPSmB E1 and CFPSmBE8.8, respectively. Antibody Y12 to endogenous Sm proteins (right-hand panel) gave a band at 28/29 kDa in all cell lines, representing endogenous SmB/SmB’. In cells from lines YFPSmBE1 and CFPSmBE8.8, additional, less intense bands were detected at 58 kDa, representing YFPSmB and CFPSmB, respectively.
