Cold Spring Harbor, N.Y. Most of the DNA in the nucleus of each of our cells is converted into RNA, but only a small fraction of these RNA molecules serve as coding templates for the synthesis of proteins. Of the remaining RNAs, known as "non-coding" RNAs (ncRNA), the functions of a scant few are known: they inhibit the activity of genes or modify them by altering the way in which DNA is packaged within cells. What the rest of them do within cells is largely a mystery.
Professor David L. Spector, Ph.D., and a team led by graduate student Hongjae Sunwoo at Cold Spring Harbor Laboratory (CSHL), have expanded our knowledge of ncRNA functions by uncovering a unique structure-building role for two ncRNA molecules. In a paper published in the March 1st issue of Genome Research, they show that ncRNAs called MENε and MENβ organize and maintain the structure of paraspeckles, a compartment within the cell's nucleus.
RNAs as structural components
Unlike its counterparts in simple organisms like yeast, the nucleus in mammalian cells has an extraordinarily complicated internal structure. In addition to the DNA-protein complex known as chromatin, the nucleus is organized with compartments such as the nucleolus, PML bodies, Cajal bodies, and many others. Cell biologists have long wondered how these compartments are organized, knowing only that each has a definite and precise form despite not being bound and contained within a membrane.
"The idea that some of these structures might somehow be supported by RNA molecules first surfaced in studies in the 1970s," according to Professor Spector. His lab found further evidence for this idea in 2005 when they showed that paraspeckles each nucleus has about 10 to 30 of these scattered around fell apart when cells were treated with an enzyme that destroys RNA. "But," Spector says, "a specific RNA molecule that gives paraspeckles their structural integrity was never found.
|Contact: Hema Bashyam|
Cold Spring Harbor Laboratory