A team of Spanish scientists from the Institute of Molecular Biology of Barcelona (IBMB), of the Higher Council for Scientific Research (CSIC), has managed to decipher how DNA makes its first and most basic folds , an advance that provides new bases for the study of how This is packaged to be able to store all the information necessary for life within a space as tiny as the cell nucleus.
As highlighted in a press release by the CSIC, thanks to this study, which has been published in the scientific journal Nature Communications, the so-called nucleosomal DNA binding number paradox has been resolved, which has been the subject of debate during the three last decades , and it has been shown that the theory described about the packaging of DNA in our cells was true.
“What had been theoretically described about how DNA folded did not coincide with the results of calculating the number of crossovers according to that theory. So either the theory was not true or the calculations were incorrect ” , explains the group’s main researcher, Joaquim Roca. The paradox “implied that we still did not really fully understand how DNA is packaged inside the cell, not even at its most elementary level,” says Roca, a professor in the Structural Biology Unit at IBMB.
In their research, these scientists have applied a new strategy in their goal of calculating with great precision the number of crossovers of the double helix in nucleosomes – the fundamental and structural unit of chromosomes – under physiological conditions. Joana Segura, a researcher at the same center and first author of the article, stresses that they have “examined the topology of more than a thousand nucleosomes within the cell”, which “has allowed them to discover a value different from the one that had been assumed to be correct until now”.
But what are nucleosomes?
They are a complex of DNA and histone proteins that constitute the first degree of packaging of DNA within the cell . In each of them, about 146 base pairs of DNA surround an octamer of histones. The distribution of this structure along thousands or millions of DNA base pairs generates a fiber similar to a string of beads, the CSIC explains in its press release.
This folding reduces the length of DNA molecules more than four times and makes them much more flexible, which is essential for them to be packaged into chromosomes and distributed in an orderly way within the cell nucleus.
In summary, the new value obtained after carrying out this research in the DNA Topology laboratory of the Structural Biology Unit solves the paradox of the binding number on DNA packaging and, at the same time, deciphers the first level of DNA folding. , which is the molecule that contains all the genetic information.
Illustration (recreation of a cell nucleus and its nucleosomes): Joaquim Roca (IBMB) / CSIC
