Table 1.

tDNAs as Insulators and Chromosome Organizers

Organism	2D tDNA Cluster	3D tDNA organization	Barrier Insulation	Enhancer Blocking	Proposed Mechanism
Budding yeast	No	Nucleolus, centromeres, nuclear pores	Yes, at native HMR	Yes, in UAS blockers	Nucleosome depletion Acetylated histones Chromosome remodelers Cohesin recruitment
Fission Yeast	Yes, Centromeres	Centromere	Yes, at native centromeres/Mat3	Unknown	Nucleosome depletion Acetylated histones Chromosome organization
Mouse	Yes, across genome	Unknown	Yes, in transgene assay and BAC reporter assay	Yes, SINES in enhancer blocking assay	Nucleosome depletion Acetylated histones Pol II transcription
Human	Yes, across genome	Intra- chromosomal cluster, Nucleolus	Yes, in transgenes assays and repressor blocking assays	Yes, tDNAs in enhancer blocking assay	Nucleosome depletion Acetylated histones CTCF and cohesin