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This Week in PNAS: Nov 23, 2010

In the PNAS Early Edition this week, researchers at Harvard Medical School and their colleagues show that the Sirt6 deletion in mice "results in striking hyperacetylation of histone H3 lysine 9 and lysine 56, two chromatin marks implicated in the regulation of gene activity and chromatin structure, in various brain regions including those involved in neuroendocrine regulation" and ultimately, obesity. Based on their observations in neural Sirt6-deleted mice, the researchers suggest that the gene "functions as a central regulator of somatic growth and plays an important role in preventing obesity by modulating neural chromatin structure and gene activity."

Investigators at Japan's National Oomuta Hospital in Fukuoka describe a "pull-down method to rapidly identify coding SNP haplotypes of triple repeat, disease-causing alleles," which they've used to target cSNP sites in mutant Huntingtin alleles with RNAi. The researchers suggest that by "using siRNAs specific to disease-linked cSNP haplotypes," they've "advanced progress toward tailor-made RNAi treatments for triplet repeat diseases."

Using gene targeting to replace Brca2 with a functionally enhanced, GFP-tagged form of the protein, researchers in the UK and Switzerland were able to measure its "diffusion in the nucleoplasm of living cells exposed to DNA breakage" via fluorescence correlation spectroscopy. "DNA damage significantly enhances the mobility of Brca2 molecules in the S/G2 phases of the cell cycle, via signaling through damage-activated protein kinases," the authors write, adding that the protein's increase in mobilization "is accompanied by increased binding within the nucleoplasm to its cargo, the Rad51 recombinase."

In another PNAS paper published online in advance this week, investigators at Sweden's Lund University, along with their colleagues in the UK, describe the "genetic landscape of high hyperdiploid childhood acute lymphoblastic leukemia," which they characterized via SNP array and subclonality analyses in a series of 74 cases. The team suggests that karyotyping mistakes are common, as nearly 80 percent of the cases they examined with SNP array analysis showed additional abnormalities than were previously reported in hyperdiploid ALL. The team also investigated the "heterogeneous pattern of secondary genetic events" observed in hyperdiploid ALL. Based on their findings, the researchers propose that the leukemic clone undergoes step-wise evolution.