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This Week in Science: Jun 29, 2012

In a paper published online in advance in Science this week, an international team led by investigators at the University of Cambridge shows that segment 3 of the influenza A virus contains a second open reading frame, X-ORF, which is accessed by way of ribosomal shifting. The team found that the product of this, PA-X, modulates virulence in a mouse model by decreasing pathogenicity. "Loss of PA-X expression leads to changes in the kinetics of the global host response, which notably includes increases in inflammatory, apoptotic, and T-lymphocyte signaling pathways," the authors write. "Thus, we have identified a previously unknown IAV protein that modulates the host response to infection, a finding with important implications for understanding IAV pathogenesis."

In another advance online publication, members of The Cancer Genome Atlas team present a single-nucleotide resolution analysis of transposable element insertions in 43 whole-genome sequence datasets for five cancer types. Among other things, the team found that "somatic L1 insertions tend to occur in genes that are commonly mutated in cancer, disrupt the expression of the target genes, and are biased toward regions of cancer-specific DNA hypomethylation, highlighting their potential impact in tumorigenesis."

University of California, Berkeley's Martin Jinek and his colleagues show in a subset of CRISPR/Cas systems that "the mature crRNA base-paired to trans-activating tracrRNA forms a two-RNA structure that directs the CRISPR-associated protein Cas9 to introduce double-stranded breaks in target DNA."

And in this week's issue, an international team led by investigators at the University of California, Davis, shows that overexpression of the transcription factor Golden 2-like, or GLK, leads to "enhanced [tomato] fruit photosynthesis gene expression and chloroplast development, leading to elevated carbohydrates and carotenoids in ripe fruit," and therefore altering taste. Ann Powell, a lead author on the tomato-taste study, tells The New York Times that an initial impetus for the project was to address the question: "Why do fruits bother being green in the first place?"