Research reveals how cells protect agai...( from the genetic blueprint contained in...)

from the genetic blueprint contained in the DNA inside the nucleus. In a process known as transcription, nuclear machines first copy the genetic code from the DNA molecules into a "transcribed" RNA molecule and then moves the RNA from the nucleus into the cell's cytoplasm, where it is "translated" into a protein. But Assmann and other researchers are discovering that RNA-binding proteins mediate a lot of cut-and-paste processing of the newly transcribed "raw" RNA before it is remodeled into "messenger" RNA and allowed to leave the nucleus carrying the blueprint for making a protein.

"A new paradigm that our research suggests is that the ABA hormone regulates the protein complement of a cell not only by controlling the initial transcription process but also by controlling the proteins involved in post-transcriptional remodeling of RNA molecules, including RNAs that encode stress-protective proteins," Assmann explains.

Another of Assmann's discoveries is that ABA regulates the formation of mysterious islands within the cell's nucleus called "nuclear speckles." Scientists do not yet know a lot about nuclear speckles in plants, but they do know that nuclear speckles in human cells contain proteins associated with the remodeling of RNA.

By expressing in plant cells the RNA-binding protein with a green fluorescent tag attached, Assmann's group was able to observe the localization of this protein within the living cell. As she watched through the microscope Assmann observed, for the first time, that ABA induced the relocation of the RNA-binding protein within the nucleus. Upon treatment of the plant tissue with ABA, the fluorescently-tagged RNA-binding proteins quickly gathered together into nuclear speckles that looked like green-glowing islands inside the cell's nucleus. "To our knowledge, such hormonally induced aggregation of RNA-remodeling proteins into nuclear speckles has not previously been observed either in plant or in animal cel
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Contact: Barbara K. Kennedy
science@psu.edu
814-863-4682
Penn State
14-Aug-2002

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