The 2017 Nobel Prize in Physiology or Medicine has been awarded to three American scientists who identified genes and proteins that regulate our biological clocks. Jeffrey C. Hall, Michael W. Young, and Michael Rosbash worked with fruit flies for decades to crack the code.
In 1984, Rosbash and Hall, working at Brandeis University in Boston, and Young at Rockefeller University in New York isolated a gene they called "period", which controlled the expression of a protein called PER. They saw that PER builds up during the hours of night, and dissipates again in daytime, so the levels oscillated over a 24-hour cycle, the basis of the "circadian rhythm" or body clock.
Importantly, they also discovered that when PER builds up in the cell, it turns off "period". So it is a self-regulating mechanism. "That was the key fundamental breakthrough," said Russell. "The appreciation of a molecular feedback loop – a gene encodes a protein which feeds back and inhibits the gene's own expression."
It wasn't clear how PER could influence its own expression, since it was unable to bind to DNA. But in 1994, Young also discovered another gene-protein pair, "timeless" and TIM, which was the missing link. He also found a third, "doubletime" and DBT, which helped control the 24-hour period.
Michael Rosbash describes the irony of the middle-of-the-night phone call he got from Stockholm that disturbed his sleep cycle.
You can read more about this research, and keep up with other Nobel Prizes as they are awarded, at the Nobel Prize website.