Figure 2.

Relationship among EBV DNA loci, their transcripts, and SC35 domains in Namalwa cells. The approach exploring DNA FISH, RNA/DNA FISH, immunocytochemistry, and DAPI staining has been used. The spatial relationship between EBV DNA loci and their transcripts is documented in A–H (as well as in I–M). The viral pre-mRNA (green) makes spot or track-like structures of various length (up to several micrometers). With the limit in z-axis resolution in mind, the majority of genes (red) occupy the periphery of the RNA environment. The small RNA accumulation associated with the DNA locus likely represents the pool of nascent transcripts (A and inset). The major fraction of cells exhibit an RNA track, which delineates the path from the gene(s) and encompasses both the nascent and released RNA (B–H). Most tracks are clear-cut polarized with respect to the position of the gene(s), with at least one locus positioned at the extremity of the track (B–E). The polarization of some tracks is less distinct (F–H). Spatial localization of viral DNA (red) and RNA (green) relative to the nuclear periphery (DAPI staining) is documented in I–K. No clear vectorial route from the gene loci to the nuclear envelope could be established. This is well documented in J, in which the track “emanates” from the gene toward the nuclear interior. A part of the second cell is seen in the bottom part of J. In I, the track emanates from the gene toward the nuclear envelope, whereas in K, the track is “parallel” to the nuclear envelope. The relative incidences of tracks seen in J and I are ∼40 and 60%, respectively. Simultaneous visualization of viral DNA sequences (red), RNA (green), and SC35 domains (AMCA; blue immunolabeling) is documented in L and M. Tracks encompassing gene loci (arrowheads) emanate toward the SC35 domain (arrow). Bars, 1.5 μm.