Figure 7: Cajal bodies orchestrate genome-wide clustering of spliceosomal and histone-related genes.

(a) Composite image detailing inter- and intra-chromosomal contact 4C interactions, gene expression changes and alternative splicing events following CB disassembly (siTCAB1) in HeLa cells for chromosomes 1, 6 and 17. The locations of gene loci of interest (RNU1, RNU2, SNORD3A, as well as HIST1, HIST2 and H3F3A) are shown. Upregulated genes (RNA-seq) are denoted by green chromosome bands (non-concordant=dark green, concordant=light green) and downregulated by red (non-concordant=dark red, concordant=light red). Baseline (siControl) expression of small RNA U genes are denoted by triangles (red=Q4 (upper, 75–100%), brown=Q3 (50–75%), purple=Q2 (25–50%) and blue=Q1 (lower, 0–25%)) Grey triangles denote the alternative splicing events, *=expression changes of genes (small RNA-seq). 4C-seq physical contact profile is shown in red (4C signal, log10 scale). (b) Proposed role of CBs (blue) in genomic organization and maintenance of tightly regulated splicing processes in HeLa cells. (c) Schematic representation of a proposed topological rearrangement of chromosome 1 by a CB (purple) and physically associated HLB (grey) resulting in regulation of gene positioning. CB- or HLB-interacting gene loci are shown in green, whereas non-interacting regions are shown in red.