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This Week in PNAS: Feb 23, 2010

In the PNAS Early Edition this week, an international research collaboration led by Chengjun Li at the University of Wisconsin-Madison describes their finding that genetic reassortment between the avian H5N1 and human H3N2 flu viruses causes hybrid strains with substantial virulence. To evaluate the pathogenic potential of these reassortant viruses, Li et al. created all 254 possible hybrids of H5N1 and H3N2 by using reverse genetics. “Some hybrids between H5N1 virus and seasonal influenza viruses were more pathogenic than the original H5N1 viruses. That is worrisome,” Yoshihiro Kawaoka, the senior author of the study said in a press release.

In another article, Wisconsin researchers evaluate the specificity spectra of DNA binding molecules by examining different classes of proteins and engineered DNA-binding molecules across the entire sequence space. “Importantly, the sequence context of a binding site significantly influences binding energetics, and utilizing the full contextual information permits greater accuracy in annotating regulatory elements within a given genome,” the team writes. The researchers suggest that their comprehensive approach could guide the creation of DNA therapeutics and elucidate the forces behind the sequence specificity of DNA binding molecules.

Research out of the University of Colorado, Boulder, this week describes the 2’(3’) aminoacylation of a small, 5-nt-long RNA enzyme with a 3-nt active center. Rebecca Turk et al. write that their observations of the “minimal requirements for regiospecific translational activity strongly support the hypothesis that minuscule RNA enzymes participated in early forms of translation.”

University of Manchester researchers report their development of riboswitches ― small-molecule dependent, protein-free, mRNA genetic switches ― that are selective for synthetic small molecules, and no longer respond to natural intracellular ligands. The team demonstrates the riboswitches’ orthogonal selectivity in vivo using x-ray crystallography and isothermal titration calorimetry techniques. They suggest that their approach may be useful to re-engineer other natural riboswitches in both prokaryotes and eukaryotes.