The Dead Sea, where Haloferax volcanii lives Wikimedia, Ian and Wendy SewellOur genetic material is packaged into chromatin—DNA wrapped around proteins called histones, then bound up in bundles called nucleosomes. This style of packaging has long been considered a hallmark of eukaryotes, a way of compressing our large genomes into manageable sizes and controlling the expression of our genes. But scientists from the University of Toronto have shown that archaea—a separate domain of life—also wrap their genomes around histones in a way that resembles eukaryotic chromatin.
“The conventional wisdom was that the purpose of chromatin was genome-packaging—fitting a 4-meter stretch of DNA into a 5-micrometer nucleus,” said the University of Toronto’s Corey Nislow, who led the new study. But archaea do not have a nucleus, and their small circular genomes are easier to package inside their cells. “If the primary role for chromatin is not packaging, it might instead be to regulate gene expression,” Nislow said.
There are two types of archaeal histones, which collectively form bundles of four and protect around 60 base pairs of DNA. By contrast, eukaryotes have four histone types that assemble into clumps of eight and protect around 147 base pairs. “[Our knowledge of these archaeal histones] is analogous to the state of the eukaryotic histone ...
