Figure 1.

Cajal bodies nucleate at chromatin regions with high target gene density. (a) CB target gene density for human chromosomes containing major sn/snoRNA gene arrays and size-matched chromosomes. Genes were binned into 10⁶ base pair (1 Mbp) windows. The positions of potential major CB nucleation sites and other notable intron-encoded small RNAs are indicated with pointers. List of U sn/snoRNA genes were acquired from publically-accessible databases and potentially includes pseudogenes and other intron-encoded sn/sno/scaRNAs that are neither expressed nor sensitive to CB disassembly by knockdown of essential CB components by siRNA. CB target gene loci include spliceosomal U snRNA, SNORD, SNORA, SCARNA and histone genes. (b) CB target gene density and (c) total gene density for all human chromosomes, normalized per 10⁶ base pairs indicates that CB target gene density is independent of total gene density (Pearson coefficient = 0.49).