Multi-scale architecture of archaeal chromosomes

Chromosome conformation capture (3C) technologies have identified topologically associating domains (TADs) and larger A/B compartments as two salient structural features of eukaryotic chromosomes. These structures are sculpted by the combined actions of transcription and structural maintenance of chromosomes (SMC) superfamily proteins. Bacterial chromosomes fold into TAD-like chromosomal interaction domains (CIDs) but do not display A/B compartment-type organization. Here, we reveal that chromosomes of Sulfolobus archaea are organized into CID-like topological domains in addition to the larger A/B compartment-type structures that we described recently. We uncover local rules governing the identity of the topological domains. We also identify long-range loop structures which provide evidence of a hub-like structure that colocalizes genes involved in ribosome biogenesis. In addition to providing high resolution description of archaeal chromosome architectures, our data provide evidence for multiple modes of organization in prokaryotic chromosomes and yield novel insight into the evolution of eukaryotic chromosome conformation. Overall design: 3C-seq and RNA-seq experiments were performed on Sulfolobus acidocaldarius and Sulfolobus islandicus.