Biologists Find Striking Similarities between Human and Archaeal Chromosomes

The similar clustering of DNA in the chromosomes of humans and Archaea is significant because certain genes activate or deactivate based upon how they’re folded, according to a paper published in the journal Cell.

Sulfolobus sp.: each cell is outlined in red; the DNA is stained blue. Image credit: Stephen Bell, Indiana University.

Sulfolobus sp.: each cell is outlined in red; the DNA is stained blue. Image credit: Stephen Bell, Indiana University.

Archaea are one of the primary domains of cellular life, and are possibly the most ancient form of life: putative fossils of archaeal cells in stromatolites have been dated to almost 3.5 billion years ago.

Like bacteria, these single-celled microorganisms are prokaryotes, meaning that they have no cell nucleus or any other organelles in their cells.

They thrive in a bewildering variety of habitats, from the familiar — soils and oceans — to the inhospitable and bizarre. They play major roles in modern-day biogeochemical cycles, and are central to debates about the origin of eukaryotic cells.

The new study, led by Indiana University’s Professor Stephen Bell, is the first to visualize the organization of DNA in archaeal chromosomes.

The study was conducted using Sulfolobus acidocaldarius and Sulfolobus islandicus — two species of Sulfolobus, a genus of Archaea that thrives at extremely high temperatures — because their physical durability allows them to be more easily used in experiments.

The key similarity between human and archaeal chromosomes was the way in which the DNA is arranged into clusters – or ‘discrete compartmentalizations’ — based upon their function.

“When we first saw the interaction patterns of the archaeal DNA, we were shocked. It looked just like what has been seen with human DNA,” Professor Bell said.

The study is also the first to describe the protein used to assemble archaeal DNA during cellular growth.

The researchers dubbed this large protein complex as coalescin due to its similarities to a protein in eukaryotes called condensin.

The advantages to the use of Archaea as a model for studying the organization of DNA during cellular growth in humans — and the relationship between that organization and the activation of genes that may trigger cancers — is their relative simplicity.

“Human cells are horrifyingly complex, and understanding the rules that govern DNA folding is extremely challenging,” Professor Bell said.

“The simplicity of Archaea means that they’ve got the potential to be a terrific model to help understand the fundamentally related — but much more complicated — cellular processes in humans.”

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Naomichi Takemata et al. 2019. Physical and Functional Compartmentalization of Archaeal Chromosomes. Cell 179 (1): 165-179; doi: 10.1016/j.cell.2019.08.036

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