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Counter Defense Strategy of Virus

12/01/2006

Counter Defense Strategy of Virus
RNA silencing evolved as a means of defense against viral pathogens. In turn, viruses have evolved a counter-defense mechanism to inhibit RNA silencing. In the December 1st issue of G&D, a team of NYC scientists, led by Dr. Nam-Hai Chua at the Rockefeller University, lend new insight into how the Cucumber mosaic virus (CMV) executes its counter-defense. The researchers found that CMV synthesizes a protein, called 2b, that binds to AGO1 (a core component of the RNA silencing pathway) to inhibit its cleavage activity, and thereby attenuate RNA silencing. Dr. Chua "expects that other viruses may use similar mechanisms. Therefore, understanding how the 2b suppressor protein functions will allow us to design novel strategies that enable crop plants to survive a variety of threatening viruses."

The Pull of Bacterial Chromosome Segregation
A new paper in the December 1st issue of G&D reveals that a mitotic-like motor powers chromosome segregation in prokaryotes. Studying the bacteria Vibrio cholerae, Drs. Michael Fogel and Matthew Waldor (Tufts University School of Medicine) determined that the chromosome-encoded Par proteins generate a pulling force – similar to that found in eukaryotic anaphase – that mediates the asymmetric segregation of bacterial DNA. Dr. Waldor emphasizes that "The presence of mitotic machines in bacteria suggests that the basic elements for eukaryotic mitosis evolved before the appearance of multicellular organisms."

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