US uncover milestone in genome's 'dark matter'

Two U.S. scientists said they discovered more on origin of genomic dark matter, non-coding RNA, which comprises more than 95 percent of the human genome. B. Franklin Pugh, the Willaman chair in Molecular Biology at Penn State University, and Bryan Venters, who is on faculty at Vanderbilt University, discovered essentially all coding and non-coding RNA originates at the same types of locations along the human genome, Penn State said Wednesday in a release. The scientists said their findings could help pinpoint exactly where complex-disease traits reside, since genetic origins of many diseases are outside of the coding region of the genome. Pugh and Venters set out to identify the precise location of the beginnings of transcription, the first step in the expression of genes into proteins but they determined where proteins that initiate transcription of non-coding RNA were located along human chromosomes. "So rather than look for the RNA product of transcription we looked for the 'initiation machine' that makes the RNA," Pugh said. "This 'machine' assembles RNA polymerase, which goes on to make RNA, which goes on to make a protein." Pugh and Venters determined non-coding initiation machines recognized the same DNA sequences as the ones at coding genes, indicating they have a specific origin and their production is regulated, Pugh said. "These non-coding RNAs have been called the 'dark matter' of the genome because, just like the dark matter of the universe, they are massive in terms of coverage ... . However, they are difficult to detect and no one knows exactly what they all are doing or why they are there," Pugh said. "Now at least we know that they are real, and not just 'noise' or 'junk.'"