HeLa cells stably expressing the BAC-encoded GFP-labeled hPrp8 snRNP and MS2-mRED protein and treated with doxycholine to express the E3 transgene. Shown is the GFP signal. Cells imaged witb a Leica ...

HeLa cells stably expressing the BAC-encoded GFP-labeled hPrp4 snRNP and MS2-mRED protein and treated with doxycholine to express the E3 transgene. Shown is the mRED signal. Cells imaged witb a Leica...

HeLa cells stably expressing the BAC-encoded GFP-labeled U170K snRNP and MS2-mRED proteins and treated with doxycholine to express the E3 transgene. Shown is the mRED signal. Cells imaged witb a Leic...

HeLa cells stably expressing the BAC-encoded GFP-labeled U2B snRNP and Ms2-mRED protein and treated with doxycholine to express the E3 transgene. Shown is the MS2-mRED signal. Cells imaged witb a Lei...

HeLa cells stably expressing the BAC-encoded GFP-labeled U1-70K snRNP and MS2-mRED protein and treated with doxycholine to express the E3 transgene. Shown is the GFP signal. Cells imaged witb a Leica...

Mouse 3T3 fibroblast shown in phase contrast (left) and immuno-stained for the nucleolar protein nucleostemin (right, green).

Mouse 3T3 fibroblast immunostained for the nucleolar protein nucleostemin (left, green) and fibrillarin (right, red) marking nucleolar fibrillar centers.

Rat NRK fibroblasts in phase contrast and stained for the nucleolar proteins nucleostemin (green) and fibrillarin (red). Panels at right show merge. Rows show different stages of mitosis, from top, ea...

Mouse 3T3 fibroblast stained for the nucleolar protein nucleostemin (left, green) and 28S rRNA (right, red).

Transmission electron micrographs showing the unusual configuration of nucleoli in Sertoli cells, with smaller, highly dense spherical bodies flanking a large central body. Upper micrograph from guin...