Researchers Solve The Crystal Structure Of Chromatin-Bound DNA In Archaea
By Yuka Suzuki | Featured Research
March 12, 2012
A Japanese study has reported the structure of how chromatin binds to DNA in archaea, a group of single-celled microorganisms that existed as far back as four billion years ago.
AsianScientist (Mar. 12, 2012) – Ever wondered how life might have looked like four billion years ago?
Japanese researchers at the RIKEN Spring-8 Center, together with colleagues in the United States, have revealed the chromatin structure of archaea, a group of organisms that thrive in harsh environments with similar conditions to those of an early Earth four billion years ago.
Currently, all forms of life on Earth are classified by a three-domain evolutionary system – eukaryotes, archaea, and bacteria.
In multicellular eukaryotes, chromatin is made up of ‘histone’ proteins that package DNA into the nucleus of the cell. An important role of the chromatin is to control the expression of genes and DNA replication, which might lead to cancer and other diseases if such processes went out of control.
Unlike eukaryotes, archaea do not possess histones, but contain two or more DNA-binding proteins that package DNA. Alba is the most prevalent archaeal chromatin protein found in every archaeal species that survive in environments with extremely high temperatures.
To investigate how Alba binds and compacts DNA into the cell nucleus, the researchers at RIKEN studied the crystal structure of the Alba2 protein bound to DNA from the archaeal organism A. pernix k1 using synchrotron radiation.
Biologists grow crystals out of the proteins they are studying so that exposure of such crystals to radiation yields the arrangement of the atoms in the protein’s molecule, hence revealing the structure of the protein. This technique, widely used in structural biology experiments, is called X-ray crystallography.
The results of the structural study revealed how the Alba2 protein forms a hollow pipe with the DNA strand running through it. The loop structure at the end of the Alba2 DNA strand, called a ‘hairpin loop,’ helps to stabilize the pipe. This loop structure arises from the pairing of complementary DNA bases from two regions within the same DNA strand.
The paper, published in the Journal of Biological Chemistry, delineates a novel mechanism for the cellular packaging of DNA, adding valuable insights into the evolution of the chromatin structure.
What is more promising is the translation of such discoveries into the knowledge of how abnormal chromatin structure contributes to cancers and gene disorders, and the design of devices that may aid in patient diagnosis and treatments.
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