Figure 6.

U7 snRNA signal is both disperse and concentrated at discrete sites that do not necessarily correspond to CBs or sites of active HIST2 loci. (A–C) A HeLa nucleus hybridized with a U7 antisense oligonucleotide (green, A and B) and stained with anti-coilin antibody R288 (red, A and C) shows that most concentrations of U7 signal coincide with CBs. However, others are completely separate from CBs (arrowheads, note one small accumulation at the nucleolar periphery, left) or localize to the edge of a CB appearing as “buds” from the signal overlapping the CB (arrow). (D–G) Triple labeling to detect U7 snRNA (green, D, E, and G), H4 RNA (red, D, F, and G), and coilin (blue, G) shows one of three active histone loci associated with concentrated U7 signal (D and insets). This association occurs at the periphery of a CB (G and insets) in most HeLa nuclei. Bars, 5 μm.