Yale Bulletin and Calendar

November 2, 2007|Volume 36, Number 9

Study shows tiny RNAs play
big role in controlling genes

A study by researchers at the Yale Stem Cell Center for the first time demonstrates that piRNAs, a recently discovered class of tiny RNAs, play an important role in controlling gene function, it was reported in the journal Nature.

Haifan Lin, director of the stem cell center and professor of cell biology at Yale School of Medicine, heads the laboratory that originally identified piRNAs. Derived mostly from so-called “junk DNA,” piRNAs had escaped the attention of generations of geneticists and molecular biologists until last year when Lin’s team discovered them in mammalian reproductive cells, and named them.

The lab’s current work suggests that pi-RNAs have crucial functions in controlling stem cell fate and other processes of tissue development.

In this study Lin and his Ph.D. student, Hang Yin, discovered more than 13,000 piRNAs in fruit flies that are associated with the protein known as Piwi. One particular piRNA, they found, forms a complex with Piwi, which then binds to chromatin, a strategic region in the genome that regulates the activity of the gene. Chromatin’s role is to package DNA so that it will fit into the cell, to strengthen the DNA to allow cell division, and to serve as a mechanism to control gene expression.

“This is important in maintaining self-renewal of stem cells,” Lin says. “These small RNAs might provide new tools to harness the behavior of stem cells and other biological processes related to diseases.”

He adds: “This finding revealed a surprisingly important role for piRNAs, as well as junk DNA, in stem cell division. It calls upon biologists to look for answers beyond the 1% of the genome with protein coding capacity to the vast land of junk DNA, which constitutes 99% of the genome.”

This research was supported by the Mather’s Foundation and the National Institutes of Health.

— By Jacqueline Weaver

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