Nobel prizes recognize things great and small: awards focus on birth of universe and the workings of cells.

The 2006 Nobel prizes in the sciences were announced early this week. U.S. scientists swept the field.

Physiology or Medicine

Eight years after revealing a mechanism that cells use to regulate protein production, a pair of U.S. scientists received the Nobel Prize in Physiology or Medicine.

Andrew Fire of the Stanford University School of Medicine and Craig Mello of the University of Massachusetts Medical School in Worcester will share the $1.4 million award for their discovery of a phenomenon since named RNA interference, or RNAi (SN: 7/2/05, p. 7). According to the Nobel assembly of the Karolinska Institute in Stockholm, the RNAi mechanism was "totally unexpected and has dramatically expanded our knowledge of gene control."

For more than 40 years, researchers had known that RNA, a single-stranded nucleic acid, carries instructions from a gene to the cell's protein-making machinery. Working in the mid-1990s with a roundworm, Fire and Mello found that double-stranded RNA with a given sequence shuts down protein production of the gene with a matching sequence. That finding explained puzzling results in previous experiments by Fire and Mello and by other research teams.

Fire and Mello published their findings on this phenomenon, called gene silencing as well as RNAi, in 1998.

Other researchers subsequently worked out the basic mechanism of RNAi. Double-stranded RNA activates cellular machinery that chops up single-stranded RNA carrying messages from the particular gene.

Furthermore, researchers have found that organisms use RNAi in a variety of ways, such as to defend themselves against viruses and to regulate gene expression during development.

When publishing their first paper on RNAi, notes Fire, he and Mello "envisioned that we'd be able to do a lot of things in worms," such as shutting off particular roundworm genes one by one to determine their function. However, other research teams soon discovered that they could use the method to muffle protein production in virtually all multicellular organisms, including fungi, plants, and animals.

Such a simple way to control proteins in experiments "has opened up a tremendous number of doors" for both basic and applied research, says physician John Rossi of City of Hope, a medical-research center in Duarte, Calif.

Rossi and other scientists also aim to turn bits of double-stranded RNA into drugs that eliminate troublesome proteins from cells. Some such drugs are in clinical trials, but none is on the market yet.

That strategy could fight AIDS, Alzheimer's disease, influenza, and other health problems, says chief scientific officer Barry Polisky of San Francisco--based Sirna Therapeutics. RNAi "has applications for all important human diseases. As amazing as that sounds, it's true," he says.

Alejandro Sanchez Alvarado of the University of Utah Health Sciences Center in Salt Lake City, who studies tissue regeneration, says that it's "terrific" that this year's Nobel prize in the life sciences was awarded for research that had no foreseeable application when Fire and Mello began their work.

Today, biologists of almost every stripe incorporate RNAi into their studies. "It's a good example of what happens when people do really good science just for the sake of doing science," Alvarado says.--C. BROWNLEE

Physics

Two astrophysicists have won the 2006 Nobel Prize in Physics for their leading roles in a satellite mission that provided convincing evidence of the validity of the Big Bang theory and first detected the seeds of galaxy formation. John C. Mather of the NASA Goddard Space Flight Center in Greenbelt, Md., and George E Smoot of the Lawrence Berkeley (Calif.) National Laboratory and the University of California, Berkeley will share the award.

In the 1970s and 1980s, Mather was "the true driving force" behind the satellite known as NASA's Cosmic Background Explorer (COBE), according to the Royal Swedish Academy of Sciences, the institute that awards the physics prize. Development of the satellite, which was expected to be put in orbit by a space shuttle, was set back by the 1986 explosion of the shuttle Challenger, but Mather steered COBE through that obstacle and others.

"I felt like I was riding on the back of a tiger," Mather recalled at a news conference on Oct. 3.

Launched by a rocket in 1989, COBE made the first precise measurements across the entire sky of the faint microwave glow that remains from the universe's fiery birth (SN: 5/2/92, p. 292). By demonstrating that that relic energy exactly fits a pattern known as a blackbody spectrum, the satellite's data bore out a crucial prediction by supporters of the Big Bang scenario.

Mather was responsible for the particular instrument--one of three on COBE--that made the blackbody measurements.

"The perfect blackbody spectrum virtually ruled out any explanation for the cosmic-microwave background other than the Big Bang," notes cosmologist Michael S. Turner of the University of Chicago.

Smoot led the development and operation of another of COBE's instruments, which discerned tiny temperature variations of the microwave background across the sky. Until then, scientists couldn't explain how the perfectly uniform ball of expanding matter of the nascent universe gave rise

to today's galaxies and clusters of galaxies.

Theorists had predicted that, in the first moments of the universe, random appearances and disappearances of elementary particles--a process predicted by quantum mechanics--could have caused sub-microscopic irregularities that suddenly grew large as space rapidly expanded.

By spotting temperature differences of a few hundred-thousandths of a kelvin, Smoot's instrument revealed the first evidence of those stretched-out quantum irregularities--the seeds of further lumpiness built up by gravitational attraction.

"The COBE images are our first look at the baby picture of the universe," says David N. Spergel of Princeton University.

Since COBE's 4-year mission, scientists have used other spacecraft, such as NASA's Wilkinson Microwave Anisotropy Probe (WMAP), to refine the microwave-background measurements and thereby gauge specific properties of the universe, such as its age and composition, with unprecedented accuracy (SN: 2/15/2003, p. 99).

"COBE showed those variations are there, so that subsequent experiments could measure them very carefully," Smoot told Science News.

Spergel, a member of the WMAP team, says he was "thrilled to hear that the COBE team was recognized."--P. WEISS

Chemistry

Continuing this year's recognition of U.S. scientists, the Royal Swedish Academy of Sciences named Roger D. Kornberg of the Stanford University School of Medicine the winner of the 2006 Nobel Prize in Chemistry. Kornberg's research uncovered fundamental details of the mechanism by which cells access the protein-making directions encoded in their genes.

In 2001, Kornberg published X-ray crystallography images that depicted how a yeast cell transfers data stored in its DNA. An enzyme called RNA polymerase latches on to the DNA and builds messenger RNA, a single-stranded bearer of the information. Kornberg's molecular snapshots, which revealed the positions of the DNA and messenger RNA within the RNA polymerase, indicated how the enzyme makes a correct copy. Once the messenger RNA is complete, the cell translates it into a protein.

Next week's issue of Science News will elaborate on Kornberg's work.--A. CUNNINGHAM