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Cardiff researcher finds chromatin in volcano

24 July 2013

An archaeal nucleosome visualised using sequence data
 An archaeal nucleosome visualised using sequence data

An international collaboration including researchers from Osaka, Kyoto and Exeter Universities, led by Dr Nicholas Kent in the Cardiff School of Biosciences has discovered that the mechanism used by human cells to package DNA into chromosomes is evolutionarily ancient and also occurs in bacteria-like cells growing in volcanic springs.

The DNA molecules encoding genomes are enormously long. The DNA in each human cell, for example, is 2 metres in length. This potential tangle of molecular spaghetti must be packaged into the cell nucleus whilst still allowing the genes encoded within to function correctly. In humans this task is fulfilled by proteins called histones, around which DNA molecules are repeatedly wrapped to form chains of structures called nucleosomes. Nucleosomes resemble beads-on-a-string. The histone beads are used as markers for gene-regulatory information and can also gather together to form spirals and loops that compact the DNA string. This intricate DNA regulation and packaging system was thought to be the preserve of complex organisms such as animals and plants. However, the team led by Dr. Nicholas Kent has now discovered a similar system in the kingdom of archaea, bacteria-like cells which often grow in extreme environments.

Dr Kent explained: “We had originally been developing DNA sequencing and computational technologies to map nucleosomes in human cells in order to understand genome structure defects that might underlie disease. However, we realised that we could also apply this technology to any cell type and decided to investigate an archaeal species that grows in volcanic springs on the island of Kodakara in Japan. To our surprise, we found histone proteins that form variably-sized sausages-on-a-string.  Humans and archaea last shared a common ancestor more than 3 billion years ago, thus these results suggest that the human DNA packing system was developed early in the evolution of life. “

The collaboration has published its results in EMBO Reports and now plans to extend this work to other unusual organisms in order to fully uncover the rules of genome packaging thereby allowing us to understand the processes that govern our own DNA structure.