Researchers at the Harvard School of Public Health and their collaborators show in this week's PNAS Early Edition that "cigarette smoking increases copy number alterations in non-small cell lung cancer." The team reports results of a genome-wide study of DNA copy number and smoking pack-years on 264 NSCLC tumors, divided into discovery and validation sets. "We found that heavy cigarette smokers ([fewer than] 60 pack-years) have significantly more copy number gains than non- or light smokers ([more than or equal to] 60 pack-years) ... especially in 8q and 12q," the authors write, later concluding that smoking-associated copy number changes "may be mediated by genome instability."
Also in the Early Edition, investigators at Zhongshan University, the Beijing Institute of Genomics, and the University of Chicago test what's known as the "toxic-error hypothesis" using miRNA genes, "because their processing errors can be directly measured by deep sequencing." The international team shows that, "like the mature miRNA, the backbone is highly conserved; the rate of sequence evolution in the backbone is negatively correlated with expression; and although conserved between distantly related species, the error rate in miRNA processing is also negatively correlated with the expression level."
Investigators at MIT and the Singapore-MIT Alliance for Research and Technology Centre this week report their study on "the effects of a uniform electric field on the conformation of single DNA molecule." The team found that "metastable states are the result of intramolecular self-entanglements induced by the electric field," which it suggests has "broad importance in DNA separations and single molecule genomics, polymer rheology, and DNA-based nanofabrication."
In another PNAS paper published online in advance this week, a team of researchers at the Institute of Human Genetics in Montpellier and elsewhere in France show that, at the metaphase stage, "Xenopus egg extracts … have a strong reprogramming activity on mouse embryonic fibroblasts." In their paper, the researchers report data to show that "mitosis is essential to make mammalian somatic nuclei prone to reprogramming and that, surprisingly, the heterologous Xenopus system has features that are conserved enough to remodel mammalian nuclei."