October 28 (HealthDay News) -- What proteins a cell makes when and where appears to be influenced by an extensive network of regulatory interactions, say researchers at the Stanford University School of Medicine.

The new research, done on yeast, concludes that certain proteins guide molecules carrying genetic instructions from a cell's nuclei to many other locations within the cell where the instructions are carried out.

The findings were published Oct. 27 in Public Library of Science -- Biology.

Proteins are the main structural components of living cells, doing most of the cell's work. They must be produced in an orderly way to fulfill the many different roles they play at different times. The question, though, has been: How do they accomplish so many various things, when virtually all of an organism's cells contain the same genes?

"If you gaze into the genome, you see lots of regions that don't code for proteins but are conserved in nature -- they remain unchanged from organism to organism over eons of evolutionary time," investigator Dan Hogan, a graduate student at the university's medical school, said in a news release issued by the school. "This suggests that these regions may be playing some important regulatory role."

The researchers found a system of regulation instigated by a class of proteins that binds to RNA. These guide the fate of most, if not all, protein-coding RNA molecules. The study showed that virtually every protein-coding RNA molecule encoded in the yeast genome appears to be bound by specific combinations of RNA-binding proteins (RBPs). These are directed to their target RNAs by short, barcode-like sequences on those RNA molecules. The team has already found more than 500 different RBPs in yeast.

"Our work suggests that what had seemed like a relatively few specialized RBPs that are involved in some specific regulatory processes instead constitute a pervasive system of biological regulation, in many ways paralleling that of transcription factors," investigator Pat Brown, Stanford professor of biochemistry, said in the news release. "Just as transcription factors are recruited to the specific sets of genes they regulate by recognizing specific DNA sequences, these RBPs are recruited to a specific set of RNAs they regulate by recognizing specific sequences in those RNA molecules."

He said no reason exists to think RBPs' regulatory activity is confined to yeast, and even more would be likely to exist in multicellular organisms, such as human beings.

SOURCE: Stanford University Medical Center, news release, Oct. 27, 2008