The intricacies of life are just mind boggling when you stop to think about them. Take, for example, the “simple” act of a fetus growing a leg. This is happening every minute of every hour in a vast array of animals throughout the world, and it relies on precise timing and activation of specific genetic markers instructing cells how to differentiate and grow.
Hopefully most anyone reading a science blog has a decent idea of how genetics work. DNA is like a blueprint that gets read by RNA, which instructs other tiny structures how to build the thousands of tiny bits and pieces that makes complex life possible. Only about two percent of the human genome, however, encodes proteins, leaving a staggering 98 percent left to do something else.
For a long time, scientists thought this “nothing else” was just that—nothing. But it turns out that most—if not perhaps all—of it does actually play a function. For example, controlling the activation of other DNA segments.
There’s still so much to learn about how the body organizes and controls its various functions that it sometimes feels like Sisyphus forever pushing a boulder up a mountainside.
But sometimes the mountain plateaus, if only for a moment.
Elizabeth Tran, assistant professor of biochemistry at Purdue University, and her colleagues recently discovered a pretty neat trick that long non-coding RNAs can do. Long non-coding RNAs are strains of RNA longer than 200 nucleotide puzzle pieces that—you guessed it—don’t code for any proteins. While there are some thousands of these genetic machines in mammals, only a small proportion have been found to be biologically relevant.
One suggested role of long non-coding RNAs was gene repression, but Tran’s study showed the opposite is true.
Yeast are famous for eating sugars and crapping out carbon dioxide, allowing bread to rise and beer to carbonate. There are many forms of sugar, though, some of which are easier to metabolize than others, as any good South Beach dieter will inform you. Yeast’s sugar of choice is glucose, but when that runs out, it has no issue switching its metabolism over to feed on another type of sugar called galactose.
In Tran’s study, the researchers found that long non-coding RNAs prepare metabolic genes to be activated swiftly when baker’s yeast needs to switch its source of energy. Yeast with long non-coding RNA begin metabolizing galactose about 30 minutes quicker than yeast without.
And while that may not seem like that much of a difference, keep in mind that yeast reproduce every 90 minutes. What if I turned on something in you that made puberty hit twice as early? I bet you’d notice a difference then.
Tran likened the difference to a sprinter getting out of the gates quicker than the competition.”One reason the runner Usain Bolt is so fast is that he developed a technique of getting out of the block really quickly,” she said. “Being able to do that means you can spread out your energy during the race – all because you started faster at the beginning.”
Humans contain upwards of 8,000 long non-coding RNAs, some of which have been linked to cancer, developmental diseases and cardiomyopathy and other non-DNA mutations in the genome. Tran said the chances are high that long non-coding RNAs play a role in human diseases, developmental defects and delays.
“Now the question becomes why long non-coding RNAs are so closely associated with development,” Tran said. “Having opened up the possibility that they’re linked to timing and not end level of gene expression is really key.”
The study, “Long Noncoding RNAs Promote Transcriptional Poising of Inducible Genes,” was published in PLOS Biology by Tran and colleagues Sara Cloutier, Siwen Wang, Wai Kit Ma and Christopher Petell.