Plant biologists discover unexpected proteins affecting ...( LA JOLLA CA - Now that high school b...)

LA JOLLA, CA - Now that high school biology students can recite that genes are made of DNA, which is transcribed into messenger RNA (mRNA), which is then translated into protein, along comes a new class of molecules, sending studentsand many scientistsscrambling for updated textbooks.

A study by Salk Institute for Biological Studies investigator Joseph Ecker, Ph.D., reported in the May 15, 2008 online issue of Developmental Cell, shows that the RNA world is more complex than imagined. Ecker and colleagues tinkered with factors that process mRNAs in the mustard weed Arabidopsis thaliana and observed affects on short, or small RNAs. Their findings could impact fields as diverse as plant pathology and cancer research.

Although they dont fit neatly into the DNA-to-mRNA-to-protein progression, small RNAs or microRNAs are the next big thing in both plant and animal molecular biology. Discovered a decade ago, numerous studies show that small RNAs put the brakes on the mRNA-to-protein step, by latching onto mRNA and blocking its translation into protein or causing its destruction, a phenomenon called RNA silencing.

Ecker, a professor in the Plant Biology Laboratory and director of the Salk Institute Genomic Analysis Laboratory, started by posing a simple genetic question. Researchers knew that eliminating either one of two proteinsone an mRNA-degrading enzyme called EIN5, and another a protein called ABH1 that binds to and protects mRNA from degradationcaused developmental defects in plants. Eckers group asked what the effects of mutating both simultaneously might be.

Aided by revolutionary deep-sequencing technology, which detects rare RNAs at high resolution, the investigators combed through the collection of all small RNAsknown as the smRNAomeand found that ein5/abh1 double mutant plants ramped up small RNA levels just enough to reveal something not seen before: the mutant plant cells were churning out small RNAs made from some
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