Junk DNA may not be so useless after all.
Scientists coined the term to describe the genetic wasteland within the human genome, or book of life, which consists of long uncharted stretches of DNA for which there is no known function.
But researchers from Harvard Medical School said on Wednesday that within junk DNA in the yeast genome they have discovered a new class of gene.
Unlike other genes, the new one does not produce a protein or enzyme to carry out its function. But when it is turned on, it regulates a neighboring gene.
“This doesn’t explain all junk DNA. It gives a potential use for some junk DNA,” Professor Fred Winston, who headed the research team, said in an interview.
“I cannot think of another regulatory gene such as this one,” he added.
There are about 30,000 to 40,000 genes in the human genome. Much of the genome consists of junk DNA which scientists are trying to decipher to determine the causes and potential treatments for human diseases.
New gene helps regulate others
The new gene called SRG1 blocks the function of the adjacent gene in the yeast genome. Winston and his team, who reported their finding in the science journal Nature, believe other genes could work in the same way and in other organisms including humans.
“We found one example of a type of regulatory gene that hasn’t been found before that might alert investigators to look for it in other cases,” Winston said.
“This type of regulation may occur in other cases throughout the biological kingdom,” he added.
The new gene works by making RNA, a cousin of DNA, which represses or turns off the adjacent gene.
“When people are looking to understand the regulation of genes from whatever organism -- humans, flies, mice, yeast -- they cannot just look for proteins that are acting there. It might be that it is simply the act of transcribing that is causing regulation,” said Winston.
The DNA alphabet consists of four letters -- A, C, G and T -- which carry instructions for making all organisms. The sequence of the letters carry the code. Each set of three letters corresponds to a single amino acid, which join up in many different combinations to make proteins.
“We want to understand the physiology behind the regulation (of the gene). It is a previously unidentified type of regulation and if we could understand how it is controlled, we will learn more about gene expression,” said Winston.