Archaeal Chromosomes Can Contain Multiple Replicons

KEY CONCEPTS
- Some archaea have multiple replication origins.
- These origins are bound by homologs of eukaryotic replication initiation factors.
Archaea are an interesting group of organisms. Like the other prokaryotes, the eubacteria, they have small, circular chromosomes that are not located within a nuclear membrane.
However, archaea transcription, translation, and replication, in many respects, more closely resemble that of eukaryotes.
Some archaea chromosomes possess multiple replication origins. Sequence motifs within these origins are recognized and bound specifically by archaeal homologs of the eukaryotic replication initiation factors Orc1 and Cdc6. These proteins bind to several sites in the origin and, in doing so, deform the DNA. In the archaeal species Sulfolobus, all three of its origins are activated within a few minutes of one another. Termination of replication is also similar to that of eukaryotes in that replicons terminate by stochastic fork collisions rather than by discrete terminator sequences as in eubacteria.