MIT biologists have discovered a mechanism that allows cells to read their own DNA in the correct direction and prevents them from copying most of the so-called “junk DNA” that makes up long stretches of our genome.
Only about 15 percent of the human genome consists of protein-coding genes, but in recent years scientists have found that a surprising amount of the junk, or intergenic DNA, does get copied into RNA - the molecule that carries DNA’s messages to the rest of the cell.
Scientists have been trying to figure out just what this RNA might be doing, if anything. In 2008, MIT researchers led by Institute Professor Phillip Sharp discovered that much of this RNA is generated through a process called divergent expression, through which cells read their DNA in both directions moving away from a given starting point.
In a new paper appearing in Nature on June 23, Sharp and colleagues describe how cells initiate but then halt the copying of RNA in the upstream, or non-protein-coding direction, while allowing it to continue in the direction in which genes are correctly read. The finding helps to explain the existence of many recently discovered types of short strands of RNA whose function is unknown.
“This is part of an RNA revolution where we’re seeing different RNAs and new RNAs that we hadn’t suspected were present in cells, and trying to understand what role they have in the health of the cell or the viability of the cell,” says Sharp, who is a member of MIT’s Koch Institute for Integrative Cancer Research. “It gives us a whole new appreciation of the balance of the fundamental processes that allow cells to function.”
Graduate students Albert Almada and Xuebing Wu are the lead authors of the paper. Christopher Burge, a professor of biology and biological engineering, and undergraduate Andrea Kriz are also authors.
Only about 15 percent of the human genome consists of protein-coding genes, but in recent years scientists have found that a surprising amount of the junk, or intergenic DNA, does get copied into RNA - the molecule that carries DNA’s messages to the rest of the cell.
Scientists have been trying to figure out just what this RNA might be doing, if anything. In 2008, MIT researchers led by Institute Professor Phillip Sharp discovered that much of this RNA is generated through a process called divergent expression, through which cells read their DNA in both directions moving away from a given starting point.
In a new paper appearing in Nature on June 23, Sharp and colleagues describe how cells initiate but then halt the copying of RNA in the upstream, or non-protein-coding direction, while allowing it to continue in the direction in which genes are correctly read. The finding helps to explain the existence of many recently discovered types of short strands of RNA whose function is unknown.
“This is part of an RNA revolution where we’re seeing different RNAs and new RNAs that we hadn’t suspected were present in cells, and trying to understand what role they have in the health of the cell or the viability of the cell,” says Sharp, who is a member of MIT’s Koch Institute for Integrative Cancer Research. “It gives us a whole new appreciation of the balance of the fundamental processes that allow cells to function.”
Graduate students Albert Almada and Xuebing Wu are the lead authors of the paper. Christopher Burge, a professor of biology and biological engineering, and undergraduate Andrea Kriz are also authors.
