Loop domains in chromosomes are anchored to:
Beyond 30 nanometer fiber, chromatin organizes into large looped domains estimated 20 to 100 kilobases each, anchored at bases to nonhistone chromosomal scaffold or nuclear matrix. Scaffold comprises topoisomerase II alpha resolving catenations, condensin SMC2/SMC4, KIF4 motor protein and lamins forming chromosome axis. Loop anchorage compacts fiber additional 40-fold achieving 700 nanometer chromatid. Centromeres provide constriction points, telomeres protect ends, nucleolus organizes rDNA repeats, but loop bases specifically attach to scaffold proteins revealed by histone-depleted metaphase
Ref: Laemmli UK 1978 Cold Spring Harbor; Alberts et al., Chapter 4: Loop Domains Anchored to Scaffold Proteins
