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 SP5 confocal microscope using a 60x 1.4NA HCX Plan Apo objective lens. From Fig 5C in Huranova et al. 2010 J Cell Biol 191:75-86.