Determinants of Chromosome Architecture: Insulator Pairing in cis and in trans.

摘要: The chromosomes of multicellular animals are organized into a series topologically independent looped domains. This domain organization is critical for the proper utilization and propagation genetic information encoded by chromosome. A special set architectural elements, called boundaries or insulators, responsible both subdividing chromatin discrete domains determining topological these Central to functions insulators homologous heterologous insulator:insulator pairing interactions. former (pairing between copies same insulator) dictates process homolog alignment in trans, while latter different insulators) defines topology cis. To elucidate principles governing functions, we use two Homie Nhomie, that flank Drosophila even skipped locus. We show insulator interactions on one other, Nhomie mediate transvection. Critically, orientation-dependent. Consistent with role homologs, self-pairing trans head-to-head. Head-to-head self-interactions cis have been reported other fly suggesting this general principle self-pairing. not only pair themselves, but each other. Heterologous Homie-Nhomie occur cis, they serve delimit chromosomal contains transcription unit its associated enhancers. loop defined properties Nhomie. Instead being head-to-head, which would generate circular loop, head-to-tail. Head-to-tail generates stem-loop, configuration much like observed classical lampbrush chromosomes. These provide mechanistic underpinning topologies within