In the August 19 issue of the journal Molecular Cell, a revolutionary discovery by biologists at UC San Diego regarding a new component in the genetic material might necessitate a revamp of the basic biology textbook!
Textbooks state that cell DNA is made up of nucleosomes, which are the basic repeating units of chromatin. Nucleosomes appear like a string of beads when genetic material is viewed under a high-powered microscope. However, a unique chromatin particle existing midway between DNA and a nucleosome has been discovered by UC San Diego biologists, which is in effect a distinctive particle of its own.
The particle has been referred to as a “pre-nucleosome” by James Kadonaga, research head and biology Professor at UC San Diego. He said, “This novel particle was found as a precursor to a nucleosome. These findings suggest that it is necessary to reconsider what chromatin is. The pre-nucleosome is likely to be an important player in how our genetic material is duplicated and used.”
According to biologists, although the microscopic view of a pre-nucleosome might make it appear like a nucleosome, it is in fact midway between DNA and a nucleosome, as determined by biochemical tests.
The pre-nucleosomes are converted into nucleosomes by the utilization of an energy molecule ATP, say researchers.
Kadonaga says, “The discovery of pre-nucleosomes suggests that much of chromatin, which has been generally presumed to consist only of nucleosomes, may be a mixture of nucleosomes and pre-nucleosomes. So, this discovery may be the beginning of a revolution in our understanding of what chromatin is.”
Anthony Carter, who supervises chromatin grants at the National Institute of General Medical Sciences of the National Institutes of Health, which funded the research says, “The packaging of DNA with histone proteins to form chromatin helps stabilize chromosomes and plays an important role in regulating gene activities and DNA replication. The discovery of a novel intermediate DNA-histone complex offers intriguing insights into the nature of chromatin and may help us better understand how it impacts these key cellular processes.”