Researchers from the Institute of life Sciences at the University of Michigan and the Medical Institute of Howard Hughes was identified as satellite DNA, which was considered “junk DNA” plays a crucial role in the Assembly of the genome. The findings of scientists, published in the journal eLife, show that the genetic “junk” plays a vital function to ensure the correct positioning of chromosomes inside a cell’s nucleus that is necessary for the survival of the cells. And this feature is, apparently, preserved in many species.
Why “junk” DNA?
Pericentromeric satellite DNA consists of very simple and often repetitive sequence of the genetic code. Although it accounts for a significant portion of our genome, satellite DNA is not contain any specific instructions for the creation of any specific proteins. Furthermore, its repetitive nature, as believed, makes the genome less stable and more vulnerable to damage or disease. Until recently, scientists believed that the “junk” or “selfish” DNA plays no role and serves no purpose.
“We could not just come to terms with the idea that it’s just genetic debris,” said Yukiko Yamashita, research Professor in the LSI and the lead author of the study. “If we don’t need and we don’t get it, evolution would probably get rid of it. But this did not happen”.
Yamashita and her colleagues decided to see what would happen if the cells will not use pericentromere satellite DNA. Because it exists in the form of long repeated sequences, scientists can’t just mutate or cut out the entire DNA from the genome. Instead, they assigned the case to the D1 protein that binds to satellite DNA.
Scientists have removed the D1 from cells is a widely used test organism, Drosophila melanogaster (fruit fly). And then found that embryonic cells — which normally become sperm or egg dies.
Further analysis showed that dying cells formed micronuclei or tiny budding outside of the kernel, which included parts of the genome. Without whole genome encapsulated in a nucleus, the cells could not survive.
Scientists believe that a protein D1 binds to satellite DNA, collecting all the chromosomes in the nucleus. If the protein D1 can not capture satellite DNA, the cell loses the ability to form complete core and dies. Further testing showed that satellite DNA is necessary for survival of cells of different types that inject DNA into the nucleus, including people.