Cienciaes.com: Data slide. | Science Podcasts

by time news September 9, 2023

September 9, 2023

2020-05-26 10:59:53

The DNA in each of our cells measures about two meters in length, although the width of this molecule is only two billionths of a meter. The two-meter length of DNA contains, in a string of four different molecules linked one behind the other – the four “letters” of DNA – all the instructions necessary to produce a functional human being and generate more than two hundred types of cells. different that make up your body. Each of these cells will keep within it almost two meters of a copy of that DNA.

It is estimated that the smallest cell in the organism can measure about five microns in diameter, that is, it is about four hundred thousand times shorter in length than the DNA housed in its chromosomes. How do you manage to keep it inside?

Like the wool of a ball, DNA can be stored inside a cell of much shorter length rolled into balls. These tangles are made up of eight central proteins, called histones, which act as the central thread of the tangle. A little less than two turns of the DNA strand are wrapped around them. Millions of these tiny tangles, called nucleosomes, are packaged with other proteins into a denser structure, called chromatin, that forms chromosomes.

Unlike the thread in a ball of wool, DNA contains information that the cell must continually access quickly to use. If information can’t be read when needed, there’s no use storing it. How do cells solve this serious difficulty?

The “letters” that are found in the nucleosome making those two turns around the histones are not accessible to these proteins, but the “letters” that are found at the intersection between two nucleosomes, in the spacer zone between them, are. To allow access to all the “letters” at some point, the DNA coiled in the nucleosomes must slide around them, thus changing the area of the nucleosome that is around the two central histones and allowing the coiled DNA to move around. move towards the intersection zone between two nucleosomes, where the “letters” can be “read”.

Recently, a research team has studied the mechanism by which a protein, called CHD4, works, which is involved in this entire process of sliding DNA around the tangles that form nucleosomes. Surprisingly, they have found that the process happens in “bumps.” The protein pushes the DNA strand towards the nucleosome and inserts “letters” into the ball, thus generating a tension that, however, initially fails to produce any movement. When between 4 and 6 “letters” have been inserted into the ball and at the end the tension is high enough, the sliding occurs abruptly, 4 or 6 letters emerge from the other part of the ball, the tension relaxes and those letters can now be “read” by cellular proteins. This happens billions of times a day on every chromosome in our cells. Is not it wonderful?

Referencia: Yichen Zhong, et al. NATURE COMMUNICATIONS (2020) 11:1519 |

Jorge Laborda, May 26, 2020.

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