Unwinding of double-stranded DNA and separating them into single strands which can be copied for cell division is an important aspect of how life works. A team of researchers at the Research Hospital of St. Jude Children’s have determined at the atomic resolution the actual structure of the machinery through which the process is driven. The study has been published in the Nature Communications journal.
According to the senior researcher of the study who termed it as one of the greatest mysteries existing in biology that how a double-stranded DNA separates to form single strands for initiating the replication process, this technique may help in figuring out how the mechanism works. Eric Enemark, Ph.D. and also an associate member of Structural Biology Department of St. Jude said that based on the crystal structure in the research, they have proposed a rotary mechanism which drives the transformation for initiating the DNA replication.
Before the process of cell division starts, the DNA must be copied in a precise manner in a method known as replication. This research focused on an enzyme that is ring-shaped and known as the minichromosome maintenance or MCM complex which plays an important role. During the process of DNA replication, the MCM complex is at the fork where the separation of the double-stranded DNA occurs to form single strands. After this, the strands are then copied for producing a new DNA molecule.
Enemark and his colleagues have created the first atomic resolution image in which the MCM complex is bound to the single-strand DNA and the other molecules which fuel the process of replication.
The image captured the important details which include the orientation of the MCM complex and the single-strand DNA. The elements depicted how the process actually works similar to a pulley system for pulling a single strand of DNA through the MCM complex following the unwinding of the DNA. Enemark said that the same mechanism can also explain how the process of DNA replication starts. Before cell division takes place, the double-stranded DNA is encircled by two separate complex enzymes of MCM.
On the basis of the new structure determined by the replication machinery, scientists have proposed that MCM complexes start to move in different directions which leads to the separation of double-stranded DNA to form single-stranded ones. He added that this particular event is the main component of cell division and it presents the essence of life in the most streamlined manner.
Research Paper: https://www.nature.com/articles/s41467-019-11074-3