FIG. 1.

Confocal optical sections of a COS cell transfected with plasmid pSVc21 containing the complete HIV-1 provirus, showing the fluorescent ISH signal for HIV-1 RNA (env intron probe) and indirect immunofluorescent signal for SC35 splicing factor. (A) The typical nucleoplasmic and cytoplasmic diffuse distribution of HIV-1 RNA is demonstrated. Large unlabeled areas correspond to nucleoli. (B) Splicing factor SC35 occurs diffusely distributed throughout the nucleoplasm as well as in several speckled regions. (C) Merged image of the signal for viral RNA (in green) and SC35 (in red) demonstrates colocalization in the nucleoplasm, while SC35-labeled speckles are mostly devoid of env intron-containing RNA. Bar, 3.0 μm.