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Pradhan, B., Kanno, T., Umeda Igarashi, M. et al. The Smc5/6 complex is a DNA loop-extruding motor. Nature (2023). https://doi.org/10.1038/s41586-023-05963-3
Imagine you had a book whose pages contained the genetic information that codes for proteins in your body. This book is your DNA. When you’re reading the book, you have to open its pages to read the information and when you have to carry the book around you close it making it compact and no longer readable. The same goes for the structure of DNA. DNA exists in two forms – a loosely packed, readable form called chromatin or a condensed, tightly packed form called chromosomes. DNA is tightly packed in chromosomes during processes such as cell division (which is important for cells to multiply and organisms to grow), where the DNA has to be transported.
Now can you imagine what might happen if you changed a few sentences in the book? It wouldn’t have the same meaning anymore. DNA has specific sequences that code for specific proteins. At certain stages, such as when DNA is compacted into chromosomes or when chromosomes are separated during cell division, these sequences may be altered leading to mutations. Mutations are caused as a result of an altered genetic sequence that does not allow a protein to be formed correctly. Since proteins are important for many life processes these mutations can cause serious diseases.
Therefore, a combination of protein molecules termed “Structural Maintenance of Chromosome” complexes or SMC complexes is extremely important. They’re like the librarians who make sure everything remains in order. They are able to ensure that the DNA sequence remains undamaged. Two such complexes’ functions have been identified. In this study, researchers from the Karolinska Institute and the Max Planck Institute for Biophysics have discovered the function of a third SMC complex called Smc5/6.
Similar to the other two SMC protein complexes, it has been seen that Smc5/6 also uses the process of DNA loop extrusion. This simply means that it uses energy to bring DNA together into symmetrical loops. The formation of these loops happens through these 3 SMC complexes in order to fold the unraveled form of DNA into a more compact form.
What is different about Smc5/6 from the other two SMC complexes is that it uses two pairs of complexes rather than one to form the loop. The two complexes attach to the DNA strand forming a small loop and then slide along the DNA causing the loop to become bigger until they receive the signal from a specific sequence of DNA to stop. This process of “loop extrusion” leads to fewer tangles in the DNA strand – which otherwise make it difficult to decode the genetic information – and fewer issues with separating chromosomes during cell division.
These researchers have been able to understand the functioning of Smc5/6 at a molecular level and are now able to establish DNA loop extrusion as a common method among animals, plants, and fungi. Furthermore, this research can be taken further to allow other scientists to now explore in even more depth the functions of this specific SMC complex and how its properties relate to this newly discovered mechanism. This discovery is important to learn about the formation of chromosomes in order to prevent the development of genetic diseases and promote the normal development of proteins. This research also has applications in the field of medicine as previous research indicates that Smc5/6 may also be able to inhibit certain viruses and protect against some types of cancer. The applications of this new discovery seem endless and though this molecule functions at such a microscopic level it may have a very large impact on the scientific and medical fields!
Works Cited:
BYJU’s. “Eukaryotic Cells- Definition, Characteristics, Structure, & Examples.” BYJUS, 2021, byjus.com/biology/eukaryotic-cells/. Accessed 1 May 2023.
“Chromosomes Fact Sheet.” Genome.gov, 15 Aug. 2020, www.genome.gov/about-genomics/fact-sheets/Chromosomes-Fact-Sheet#:~:text=is%20a%20chromosome%3F-. Accessed 1 May 2023.
“Genetic Diseases | BioNinja.” Bioninja.com.au, 2019, ib.bioninja.com.au/standard-level/topic-3-genetics/34-inheritance/genetic-diseases.html. Accessed 1 May 2023.
“How Does DNA Fold? The Loop Extrusion Model.” Www.youtube.com, 20 Oct. 2015, www.youtube.com/watch?v=Tn5qgEqWgW8. Accessed 30 Apr. 2023.
Karolinska Institutet. “New Mechanism for DNA Folding.” ScienceDaily, 19 Apr. 2023, www.sciencedaily.com/releases/2023/04/230419125049.htm. Accessed 1 May 2023.
Liu, Paul. “Chromatin.” Genome.gov, 28 Apr. 2023, www.genome.gov/genetics-glossary/Chromatin#:~:text=Chromatin%20refers%20to%20a%20mixture. Accessed 1 May 2023.
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