Washington, Nov 5 : What was earlier considered to be "junk" DNA has now been found to be an important ingredient distinguishing humans from other species, say scientists at the Genome Institute of Singapore (GIS).
Over 50 percent of human DNA is designated as "junk" as it consists of copies of nearly identical sequences, the major source of which is internal viruses that have inserted themselves throughout the genome at various times during mammalian evolution.
By using the latest sequencing technologies, scientists proved that a large number of transcription factors-master proteins that control the expression of other genes-bind specific repeat elements.
It was shown that almost18-33 percent of the binding sites of five key transcription factors with important roles in cancer and stem cell biology are embedded in distinctive repeat families.
During evolution, the researchers said, the repeats were dispersed within different species, and created new regulatory sites throughout these genomes.
Therefore, the set of genes controlled by these transcription factors may significantly differ from species to species and may be a major driver for evolution.
The scientists established the fact that the repeats are anything but "junk DNA," as they offer a great source of evolutionary variability and might hold the key to some of the important physical differences that distinguish humans from all other species.
The research also highlighted the functional importance of portions of the genome that are rich in repetitive sequences.
"Because a lot of the biomedical research use model organisms such as mice and primates, it is important to have a detailed understanding of the differences between these model organisms and humans in order to explain our findings," said Guillaume Bourque, Ph.D., GIS Senior Group Leader and lead author of the Genome Research paper.
He added: "Our research findings imply that these surveys must also include repeats, as they are likely to be the source of important differences between model organisms and humans," added Dr. Bourque. "The better our understanding of the particularities of the human genome, the better our understanding will be of diseases and their treatments."
The study is published in the latest issue of Genome Research.