Claim: Biology texts may need to be revised

Posted by Chris Nova

Basic biology textbooks may require some major revisions soon. That’s because biologists at UC San Diego have discovered some new information about our basic genetic material.  

College students are familiar with the "new edition" scam, but this actually could be a situation where the printing of a new book is necessary.
    
The textbooks state that chromatin, the natural state of DNA in the cell, is made of nucleosomes. They also label nucleosomes as the basic repeating unit of chromatin.
    
When looked at with a high-powered microscope, nucleosomes have the appearance of beads on a string. However in the August 19th issue of the journal Molecular Cell, UC San Diego biologists describe their discovery of a new chromatin particle halfway between DNA and a nucleosome. Although it looks like a nucleosome, they say, it is actually a separate particle of its own.
    
"This novel particle was found as a precursor to a nucleosome," said James Kadonaga, a professor of biology at UC San Diego who led the research team and calls the particle a "pre-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," he said.

The scientists claim that even though the pre-nucleosome may look like a nucleosome under the microscope, biochemical tests have proven it is halfway between DNA and nucleosome.

The researchers say believe the pre-nucleosomes are changed into nucleosomes by a motor protein that utilizes the energy molecule ATP.

"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," said Kadonaga. 

"So, this discovery may be the beginning of a revolution in our understanding of what chromatin is."

Anthony Carter, who oversees  chromatin grants at the National Institute of General Medical Sciences of the National Institutes of Health, which funded the research, expressed similar sentiments.

"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."